#include <bits/stdc++.h>
using namespace std;
double x[101], y[101];
int main() {
  int n, k;
  scanf("%d%d", &n, &k);
  double sum = 0;
  scanf("%lf %lf", &x[0], &y[0]);
  for (int i = 1; i < n; i++) {
    scanf("%lf %lf", &x[i], &y[i]);
    sum += sqrt((x[i] - x[i - 1]) * (x[i] - x[i - 1]) +
                (y[i] - y[i - 1]) * (y[i] - y[i - 1]));
  }
  printf("%.9lf\n", sum * double(k) / 50.0);
  return 0;
}
