#include <bits/stdc++.h>
using namespace std;
float a[105][2] = {0};
float diatant(float x1, float x2, float y1, float y2) {
  float s;
  s = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
  return s;
}
int main() {
  int n, k, i;
  float s = 0;
  cin >> n >> k;
  for (i = 0; i < n; i++) cin >> a[i][0] >> a[i][1];
  for (i = 0; i < n - 1; i++) {
    s = s + diatant(a[i][0], a[i + 1][0], a[i][1], a[i + 1][1]);
  }
  s = (s / 50) * k;
  printf("%.9f\n", s);
  return 0;
}
