#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, k, x1, y1, x2, y2;
  long double s = 0;
  scanf("%d %d", &n, &k);
  scanf("%d %d", &x1, &y1);
  for (int i = 1; i < n; i++) {
    scanf("%d %d", &x2, &y2);
    s += (long double)sqrt((long double)(x2 - x1) * (x2 - x1) +
                           (long double)(y2 - y1) * (y2 - y1));
    x1 = x2;
    y1 = y2;
  }
  printf("%.6Lf", s * (long double)k / (long double)50);
  return 0;
}
