#include <bits/stdc++.h>
using namespace std;
int main() {
  int x, y, n, tx, ty, m;
  scanf("%d %d", &n, &m);
  double res = 0;
  for (int i = 0; i < n; i++) {
    scanf("%d %d", &x, &y);
    if (i == 0) {
      tx = x, ty = y;
      continue;
    }
    res = res + sqrt(((x - tx) * (x - tx)) + ((y - ty) * (y - ty)));
    tx = x, ty = y;
  }
  if (n == 1) {
    res = res + abs(x - y);
    printf("%.9f\n", res);
  } else {
    printf("%.9f\n", (res / 50.0) * m);
  }
  return 0;
}
