#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 5;
const long long MOD = 1e9 + 7;
const double eps = 1e-7;
int N, M, K, Q, T;
long long gcd(long long a, long long b) {
  if (b == 0LL) return a;
  return gcd(b, a % b);
}
double X[110], Y[110];
int main() {
  int i, j;
  scanf("%d%d", &N, &K);
  for (i = 1; i <= N; ++i) {
    scanf("%lf%lf", &X[i], &Y[i]);
  }
  double sum = 0.0;
  for (i = 2; i <= N; ++i) {
    double x = X[i] - X[i - 1];
    double y = Y[i] - Y[i - 1];
    double l = x * x + y * y;
    l = sqrt(l);
    sum += l;
  }
  printf("%.7lf", (double)K * sum / 50.0);
  return 0;
}
