#include <bits/stdc++.h>
int main(void) {
  int i, n, k, x, y, xp, yp;
  double d = 0.;
  scanf("%d %d\n", &n, &k);
  scanf("%d %d\n", &xp, &yp);
  for (i = 1; i < n; i++) {
    scanf("%d %d\n", &x, &y);
    d += sqrt(pow(x - xp, 2) + pow(y - yp, 2));
    xp = x;
    yp = y;
  }
  printf("%.9f\n", d * k / 50.);
  return 0;
}
