#include <bits/stdc++.h>   using namespace std;   template <class T>   T gcd(T a, T b) {     return (b != 0 ? gcd<T>(b, a % b) : a);   }   template <class T>   T lcm(T a, T b) {     return (a / gcd<T>(a, b) * b);   }   template <class T>   inline bool read(T &x) {     int c = getchar();     int sgn = 1;     while (~c && c <  0  || c >  9 ) {       if (c ==  - ) sgn = -1;       c = getchar();     }     for (x = 0; ~c &&  0  <= c && c <=  9 ; c = getchar()) x = x * 10 + c -  0 ;     x *= sgn;     return ~c;   }   const int INF = 2000000009;   const int MX = 100005;   const long double EPS = 1e-9;   const int MOD = 1000000007;   struct PT {     long double x, y;     PT() {}     PT(long double x, long double y) : x(x), y(y) {}     PT operator+(const PT &p) const { return PT(x + p.x, y + p.y); }     PT operator-(const PT &p) const { return PT(x - p.x, y - p.y); }     PT operator*(long double c) const { return PT(x * c, y * c); }     PT operator/(long double c) const { return PT(x / c, y / c); }   };   long double cross(PT a, PT b) { return a.x * b.y - a.y * b.x; }   long double dot(PT a, PT b) { return a.x * b.x + a.y * b.y; }   long double area2(PT a, PT b, PT c) {     return cross(a, b) + cross(b, c) + cross(c, a);   }   long double dist2(PT a, PT b) { return dot(b - a, b - a); }   inline int sign(long double a) {     int ret = (a < -EPS) ? -1 : ((a > EPS) ? 1 : 0);     return ret;   }   struct Line {     PT v;     long double a, b, c;     Line() {}     Line(PT p, PT q) : v(q - p), a(-v.y), b(v.x), c(cross(v, p)) {}     long double side(PT p) { return cross(v, p) - c; }   };   long double commonLength(vector<PT> &p, PT a, PT b) {     Line l = Line(a, b);     long double ans = 0.0;     int n = p.size();     p.push_back(p[0]);     vector<pair<long double, int> > vec;     for (int i = 0; i < n; i++) {       int s1 = sign(cross(b - a, p[i] - a));       int s2 = sign(cross(b - a, p[i + 1] - a));       if (s1 == s2) continue;       Line t = Line(p[i], p[i + 1]);       PT inter = (t.v * l.c - l.v * t.c) / cross(l.v, t.v);       long double tmp = dot(inter, l.v);       int f;       if (s1 > s2)         f = s1 && s2 ? 2 : 1;       else         f = s1 && s2 ? -2 : -1;       vec.push_back(make_pair(tmp, f));     }     sort(vec.begin(), vec.end());     for (int i = 0, j = 0; i + 1 < (int)vec.size(); i++) {       j += vec[i].second;       if (j) ans += vec[i + 1].first - vec[i].first;     }     ans = ans / sqrt(dot(l.v, l.v));     p.pop_back();     return ans;   }   int main() {     int n = ({       int a;       read(a);       a;     }),         m = ({           int a;           read(a);           a;         });     vector<PT> pol;     for (int i = 0; i < n; i++) {       long double x = ({         long double a;         scanf( %Lf , &a);         a;       }),                   y = ({                     long double a;                     scanf( %Lf , &a);                     a;                   });       pol.push_back(PT(x, y));     }     while (m--) {       PT a, b;       a.x = ({         long double a;         scanf( %Lf , &a);         a;       }),       a.y = ({         long double a;         scanf( %Lf , &a);         a;       }),       b.x = ({         long double a;         scanf( %Lf , &a);         a;       }),       b.y = ({         long double a;         scanf( %Lf , &a);         a;       });       printf( %.8Lf n , commonLength(pol, a, b));     }     return 0;   }   