#include <bits/stdc++.h>
float dist(int a, int b, int c, int d) {
  int x, y, z;
  x = pow((c - a), 2);
  y = pow((d - b), 2);
  return sqrt(x + y);
}
int main() {
  int n, k, x, y, a, b;
  float sum = 0;
  scanf("%d %d", &n, &k);
  scanf("%d %d", &a, &b);
  n = n - 1;
  while (n--) {
    scanf("%d %d", &x, &y);
    sum += dist(a, b, x, y);
    a = x;
    b = y;
  }
  sum = sum * k;
  sum = sum / 50;
  printf("%0.9f\n", sum);
  return 0;
}
