#include <bits/stdc++.h>
using namespace std;
int i, n, k;
double jumlah, x[101], y[101];
int main() {
  scanf("%d %d", &n, &k);
  for (i = 1; i <= n; ++i) {
    scanf("%lf %lf", &x[i], &y[i]);
  }
  for (i = 1; i < n; ++i) {
    jumlah += sqrt(((x[i] - x[i + 1]) * (x[i] - x[i + 1])) +
                   ((y[i] - y[i + 1]) * (y[i] - y[i + 1])));
  }
  jumlah = ((jumlah / 50) * k);
  printf("%.9lf\n", jumlah);
}
