Ternary Search

   /// learnt from https://codeforces.com/contest/394/submission/13185760
   
   long double dist=1e100 ;

    Point nw=rp ;

    for(int i=0;i<m;++i){
        long double l=0 , r=1 , m1 , m2 ;
        for(int it=1;it<=100;++it){
            m1=l*.51+r*.49 ;     
            m2=l*.49+r*.51 ;
            Point p1=yo[i]+(yo[i+1]-yo[i])*m1 ;
            Point p2=yo[i]+(yo[i+1]-yo[i])*m2 ;
            long double v1=(p1-rp).dis() ;
            long double v2=(p2-rp).dis() ;
            if(v1<v2)
                r=m2 ;
            else
                l=m1 ;
        }
        Point now=yo[i]+(yo[i+1]-yo[i])*(l+r)*.5 ;
        if((now-rp).dis()<dist)
            dist=(now-rp).dis() , nw=now ;
    }

/// learnt from https://codeforces.com/contest/98/submission/57618653 


double ternary_search(double lo,double hi){
while(lo+EPS<=hi){
    double m1=(lo*2.0+hi)/3.0 ;
    double m2=(lo+hi*2.0)/3.0 ;

    double v1=val(m1) ;
    double v2=val(m2) ;

    if(v1<v2)
        hi=m2 ;
    else
        lo=m1 ;
}
return val((lo+hi)/2.0) ;
}