#include <bits/stdc++.h>
using namespace std;
long long pow(long long a, long long b) {
  if (b == 0) {
    return 1;
  }
  if (b % 2 == 0) {
    return pow((a % 1000000007) * (a % 1000000007), b / 2) % 1000000007;
  } else {
    return (a % 1000000007) *
           (pow((a % 1000000007) * (a % 1000000007), (b - 1) / 2) % 1000000007);
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int i, j, k, n;
  cin >> n >> k;
  double x[n], y[n];
  for (i = 0; i < n; i++) {
    cin >> x[i] >> y[i];
  }
  double ans = 0.000000000;
  for (i = 1; i < n; i++) {
    ans += sqrt((x[i] - x[i - 1]) * (x[i] - x[i - 1]) +
                (y[i] - y[i - 1]) * (y[i] - y[i - 1]));
  }
  double f = (ans * double(k)) / (50.0000000000);
  cout << fixed << setprecision(10) << f << "\n";
}
