#include <bits/stdc++.h>
int main() {
  int x[1000], y[1000];
  int n, i, j, k;
  double waste, time;
  while (scanf("%d %d", &n, &k) != EOF) {
    for (i = 0; i < n; i++) {
      scanf("%d %d", &x[i], &y[i]);
    }
    for (i = 0, time = 0.0, waste = 0.0; i < n - 1; i++) {
      waste += sqrt((x[i] - x[i + 1]) * (x[i] - x[i + 1]) +
                    (y[i] - y[i + 1]) * (y[i] - y[i + 1]));
    }
    waste *= k;
    time = waste / 50.0;
    printf("%.9lf\n", time);
  }
}
