#include <bits/stdc++.h>
int main() {
  int n, k, i;
  double t, z, a, b, d = 0;
  scanf("%d %d", &n, &k);
  int x[n], y[n];
  for (i = 0; i < n; i++) {
    scanf("%d %d", &x[i], &y[i]);
  }
  for (i = 1; i < n; i++) {
    a = x[i - 1] - x[i];
    b = y[i - 1] - y[i];
    a = pow(a, 2);
    b = pow(b, 2);
    z = a + b;
    z = sqrt(z);
    d = d + z;
  }
  t = (d / 50) * k;
  printf("%.9lf", t);
  return 0;
}
