#include <bits/stdc++.h>
using namespace std;
const int maxn = 105;
int x[maxn], y[maxn];
int n, k;
double getDis(int x1, int y1, int x2, int y2) {
  return sqrt(double((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)));
}
int main() {
  int i;
  while (scanf("%d%d", &n, &k) != EOF) {
    for (i = 1; i <= n; i++) scanf("%d%d", &x[i], &y[i]);
    double ans = 0;
    for (i = 2; i <= n; i++) ans += getDis(x[i], y[i], x[i - 1], y[i - 1]) / 50;
    printf("%.9f\n", ans * k);
  }
  return 0;
}
