#include <bits/stdc++.h>
using namespace std;
int main() {
  double l = 0, t;
  int n, m, x, y, a, b, i;
  scanf("%d%d", &n, &m);
  scanf("%d%d", &x, &y);
  for (i = 0; i < n - 1; ++i) {
    scanf("%d%d", &a, &b);
    l += sqrt((a - x) * (a - x) * 1.0 + (b - y) * (b - y) * 1.0);
    x = a;
    y = b;
  }
  printf("%.15lf\n", l / 50.0 * m);
}
