F.cpp

#include<bits/stdc++.h>
#define rg register
#define file(x)freopen(x".in","r",stdin);freopen(x".out","w",stdout)
#ifndef ATCODER_MAXFLOW_HPP
#define ATCODER_MAXFLOW_HPP 1

#include <algorithm>
#include <cassert>
#include <limits>
#include <queue>
#include <vector>
#ifndef ATCODER_INTERNAL_QUEUE_HPP
#define ATCODER_INTERNAL_QUEUE_HPP 1

#include <vector>

namespace atcoder {

namespace internal {

template <class T> struct simple_queue {
    std::vector<T> payload;
    int pos = 0;
    void reserve(int n) { payload.reserve(n); }
    int size() const { return int(payload.size()) - pos; }
    bool empty() const { return pos == int(payload.size()); }
    void push(const T& t) { payload.push_back(t); }
    T& front() { return payload[pos]; }
    void clear() {
        payload.clear();
        pos = 0;
    }
    void pop() { pos++; }
};

}  // namespace internal

}  // namespace atcoder

#endif  // ATCODER_INTERNAL_QUEUE_HPP


namespace atcoder {

template <class Cap> struct mf_graph {
  public:
    mf_graph() : _n(0) {}
    explicit mf_graph(int n) : _n(n), g(n) {}

    int add_edge(int from, int to, Cap cap) {
        assert(0 <= from && from < _n);
        assert(0 <= to && to < _n);
        assert(0 <= cap);
        int m = int(pos.size());
        pos.push_back({from, int(g[from].size())});
        int from_id = int(g[from].size());
        int to_id = int(g[to].size());
        if (from == to) to_id++;
        g[from].push_back(_edge{to, to_id, cap});
        g[to].push_back(_edge{from, from_id, 0});
        return m;
    }

    struct edge {
        int from, to;
        Cap cap, flow;
    };

    edge get_edge(int i) {
        int m = int(pos.size());
        assert(0 <= i && i < m);
        auto _e = g[pos[i].first][pos[i].second];
        auto _re = g[_e.to][_e.rev];
        return edge{pos[i].first, _e.to, _e.cap + _re.cap, _re.cap};
    }
    std::vector<edge> edges() {
        int m = int(pos.size());
        std::vector<edge> result;
        for (int i = 0; i < m; i++) {
            result.push_back(get_edge(i));
        }
        return result;
    }
    void change_edge(int i, Cap new_cap, Cap new_flow) {
        int m = int(pos.size());
        assert(0 <= i && i < m);
        assert(0 <= new_flow && new_flow <= new_cap);
        auto& _e = g[pos[i].first][pos[i].second];
        auto& _re = g[_e.to][_e.rev];
        _e.cap = new_cap - new_flow;
        _re.cap = new_flow;
    }

    Cap flow(int s, int t) {
        return flow(s, t, std::numeric_limits<Cap>::max());
    }
    Cap flow(int s, int t, Cap flow_limit) {
        assert(0 <= s && s < _n);
        assert(0 <= t && t < _n);
        assert(s != t);

        std::vector<int> level(_n), iter(_n);
        internal::simple_queue<int> que;

        auto bfs = [&]() {
            std::fill(level.begin(), level.end(), -1);
            level[s] = 0;
            que.clear();
            que.push(s);
            while (!que.empty()) {
                int v = que.front();
                que.pop();
                for (auto e : g[v]) {
                    if (e.cap == 0 || level[e.to] >= 0) continue;
                    level[e.to] = level[v] + 1;
                    if (e.to == t) return;
                    que.push(e.to);
                }
            }
        };
        auto dfs = [&](auto self, int v, Cap up) {
            if (v == s) return up;
            Cap res = 0;
            int level_v = level[v];
            for (int& i = iter[v]; i < int(g[v].size()); i++) {
                _edge& e = g[v][i];
                if (level_v <= level[e.to] || g[e.to][e.rev].cap == 0) continue;
                Cap d =
                    self(self, e.to, std::min(up - res, g[e.to][e.rev].cap));
                if (d <= 0) continue;
                g[v][i].cap += d;
                g[e.to][e.rev].cap -= d;
                res += d;
                if (res == up) return res;
            }
            level[v] = _n;
            return res;
        };

        Cap flow = 0;
        while (flow < flow_limit) {
            bfs();
            if (level[t] == -1) break;
            std::fill(iter.begin(), iter.end(), 0);
            Cap f = dfs(dfs, t, flow_limit - flow);
            if (!f) break;
            flow += f;
        }
        return flow;
    }

    std::vector<bool> min_cut(int s) {
        std::vector<bool> visited(_n);
        internal::simple_queue<int> que;
        que.push(s);
        while (!que.empty()) {
            int p = que.front();
            que.pop();
            visited[p] = true;
            for (auto e : g[p]) {
                if (e.cap && !visited[e.to]) {
                    visited[e.to] = true;
                    que.push(e.to);
                }
            }
        }
        return visited;
    }

  private:
    int _n;
    struct _edge {
        int to, rev;
        Cap cap;
    };
    std::vector<std::pair<int, int>> pos;
    std::vector<std::vector<_edge>> g;
};

}  // namespace atcoder

#endif  // ATCODER_MAXFLOW_HPP

using namespace std;

const long long eps=1e8;
const int maxn=1e3+10;
const int maxm=2e3+10;

int n,m;
struct Edge{
	int x,y;
	long long a,b,c,d;
	inline void read()
	{
		scanf("%d %d %lld %lld %lld %lld",&x,&y,&a,&b,&c,&d);
		b*=eps,d*=eps;
	}
}E[maxm];

inline long long calc(long long t)
{
	static long long deg[maxn];
	for(rg int i=1;i<=n;i+=1)deg[i]=0;
	atcoder::mf_graph<long long>graph(n+2);
	for(rg int i=1;i<=m;i+=1)
	{
		auto [x,y,a,b,c,d]=E[i];
		long long Left=a*t+b,Right=c*t+d;
		graph.add_edge(x,y,Right-Left);
		deg[x]-=Left,deg[y]+=Left;
	}
	long long sum=0;
	for(rg int i=1;i<=n;i+=1)
		if(deg[i]>=0)graph.add_edge(0,i,deg[i]),sum+=deg[i];
		else graph.add_edge(i,n+1,-deg[i]);
	return sum-graph.flow(0,n+1);
}
inline int process(long long St)
{
	long long L=St,R=St;
	for(rg int i=30;i>=0;i-=1)
		if(L>=(1<<i)&&calc(L-(1<<i))==0)L-=1<<i;
	for(rg int i=30;i>=0;i-=1)
		if(R+(1<<i)<=eps&&calc(R+(1<<i))==0)R+=1<<i;
	printf("%.6lf\n",1.*(R-L)/eps);
	return 0;
}

int main()
{
	scanf("%d %d",&n,&m);
	for(rg int i=1;i<=m;i+=1)E[i].read();
	long long Left=0,Right=eps;
	while(Left<=Right)
	{
		long long len=(Right-Left)/3;
		long long mid1=Left+len,mid2=Right-len;
		long long Val1=calc(mid1),Val2=calc(mid2);
		if(!Val1)return process(mid1);
		if(!Val2)return process(mid2);
		if(Val1<=Val2)Right=mid2-1;
		else Left=mid1+1;
	}
	puts("0.0000000");
	return 0;
}