#include <bits/stdc++.h>
using namespace std;
int n, k;
int x[100500], y[100500];
double ans;
int main() {
  scanf("%d", &n);
  ;
  scanf("%d", &k);
  ;
  for (int i = 1; i <= n; i++) {
    scanf("%d", &x[i]);
    ;
    scanf("%d", &y[i]);
    ;
  }
  for (int i = 2; i <= n; i++) {
    double q = sqrt(pow(x[i] - x[i - 1], 2) + pow(y[i] - y[i - 1], 2));
    ans += q / 50;
  }
  cout << fixed << setprecision(9) << ans * k;
  return 0;
}
