#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  int x0, y0;
  double len = 0;
  cin >> n >> k;
  cin >> x0 >> y0;
  while (--n) {
    int x, y;
    cin >> x >> y;
    int dx = x - x0;
    int dy = y - y0;
    len += sqrt((double)(dx * dx + dy * dy));
    x0 = x;
    y0 = y;
  }
  len *= k;
  len /= 50.0;
  printf("%.6lf\n", len);
  return (0);
}
