#include <bits/stdc++.h>
int main() {
  double lx, ly, x, y, k, sum = 0;
  int n;
  scanf("%d %lf", &n, &k);
  scanf("%lf %lf", &lx, &ly);
  while (--n) {
    scanf("%lf %lf", &x, &y);
    sum += sqrt((x - lx) * (x - lx) + (y - ly) * (y - ly));
    lx = x;
    ly = y;
  }
  printf("%lf", sum / 50.0 * k);
  return 0;
}
