#include <bits/stdc++.h>
using namespace std;
long long GCD(long long a, long long b) {
  while (b) {
    a %= b;
    swap(a, b);
  }
  return a;
}
int main() {
  int n, k, i;
  long double x, y, xant, yant;
  scanf("%d%d", &n, &k);
  double sol = 0;
  for (i = 0; i < n; i++) {
    cin >> x >> y;
    if (i) sol += sqrt((x - xant) * (x - xant) + (y - yant) * (y - yant));
    xant = x, yant = y;
  }
  sol = (sol * (long double)k) / 50.0;
  printf("%.9lf\n", sol);
  return 0;
}
