#include <bits/stdc++.h>   using namespace std;   long long GCD(long long a, long long b) {     while (b) {       a %= b;       swap(a, b);     }     return a;   }   int main() {     int n, k, i;     long double x, y, xant, yant;     scanf( %d%d , &n, &k);     double sol = 0;     for (i = 0; i < n; i++) {       cin >> x >> y;       if (i) sol += sqrt((x - xant) * (x - xant) + (y - yant) * (y - yant));       xant = x, yant = y;     }     sol = (sol * (long double)k) / 50.0;     printf( %.9lf n , sol);     return 0;   }   