#include <bits/stdc++.h>   using namespace std;   int main() {     ios::sync_with_stdio(false);     cin.tie(0);     double n, k;     cin >> n >> k;     double a, b;     cin >> a >> b;     n--;     double len = 0;     while (n--) {       double x, y;       cin >> x >> y;       len += ((double)sqrt(pow(x - a, 2) + pow(y - b, 2)));       a = x;       b = y;     }     len *= k;     cout << fixed << setprecision(9) << len / (double)50 <<   n ;   }   