#include <bits/stdc++.h>
int main() {
  int n, k, x[101], y[101];
  while (~scanf("%d %d", &n, &k)) {
    for (int i = 0; i < n; i++) {
      scanf("%d %d", &x[i], &y[i]);
    }
    double sum = 0;
    for (int i = 1; i < n; i++) {
      sum += sqrt((x[i] - x[i - 1]) * (x[i] - x[i - 1]) +
                  (y[i] - y[i - 1]) * (y[i] - y[i - 1]));
    }
    printf("%.9f\n", sum / 50 * k);
  }
  return 0;
}
