#include <bits/stdc++.h>   using namespace std;   int main() {     int N, K;     cin >> N >> K;     double res = 0;     long double t1x, t1y, t2x, t2y;     cin >> t1x >> t1y;     for (int i = 1; i < N; ++i) {       t2x = t1x;       t2y = t1y;       cin >> t1x >> t1y;       res += sqrt((t1x - t2x) * (t1x - t2x) + (t1y - t2y) * (t1y - t2y));     }     printf( %.15lf n , res * K / 50);     return 0;   }   