#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:67108864")
using namespace std;
void solution();
int main() {
  solution();
  return EXIT_SUCCESS;
}
double length(pair<int, int> X, pair<int, int> Y) {
  return sqrt(pow(X.first - Y.first, 2.0) + pow(X.second - Y.second, 2.0));
}
void solution() {
  int N, K, V = 50;
  double sum = 0;
  cin >> N >> K;
  vector<pair<int, int> > vctr(N);
  for (int i = 0; i < N; cin >> vctr[i].first >> vctr[i].second, ++i)
    ;
  for (int i = 0; i < N - 1; sum += length(vctr[i], vctr[i + 1]), ++i)
    ;
  cout << fixed << setprecision(9) << sum * K / V << endl;
}
