#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k;
  double sum = 0, x, y, oldx, oldy;
  scanf("%d %d", &n, &k);
  scanf("%lf %lf", &oldx, &oldy);
  for (int i = 1; i < n; i++) {
    scanf("%lf %lf", &x, &y);
    sum += sqrt(pow(abs(x - oldx), 2) + pow(abs(y - oldy), 2));
    oldx = x;
    oldy = y;
  }
  printf("%.9lf", sum * k / 50);
}
