#include <bits/stdc++.h>
struct {
  int x, y;
} a[1000], b[1000];
int main() {
  int i, n, k;
  double s, q;
  while (~scanf("%d%d", &n, &k)) {
    s = 0;
    for (i = 0; i < n; i++) {
      scanf("%d%d", &a[i].x, &a[i].y);
    }
    for (i = 0; i < n - 1; i++) {
      b[i].y = a[i + 1].y - a[i].y;
      b[i].x = a[i + 1].x - a[i].x;
      b[i].y = pow(b[i].y, 2);
      b[i].x = pow(b[i].x, 2);
      q = b[i].x + b[i].y;
      q = sqrt(q);
      s += q;
    }
    s = s * k / 50.0;
    printf("%.9lf\n", s);
  }
  return 0;
}
