#include <bits/stdc++.h>
using namespace std;
int a[1000006];
int main() {
  int i, j;
  double x, y, x1, y1;
  int k;
  double l;
  int n;
  while (~scanf("%d%d", &n, &k)) {
    l = 0.0;
    scanf("%lf%lf", &x, &y);
    for (i = 1; i < n; i++) {
      scanf("%lf%lf", &x1, &y1);
      x = (x1 - x) * (x1 - x);
      y = (y1 - y) * (y1 - y);
      l += sqrt(x + y);
      x = x1;
      y = y1;
    }
    l = l * 1.0 / 50;
    l *= k;
    printf("%.9lf\n", l);
  }
  return 0;
}
