#include <bits/stdc++.h>
int main() {
  int n, k, i, j;
  scanf("%d%d", &n, &k);
  int a[n][2];
  for (i = 0; i < n; i++) {
    for (j = 0; j < 2; j++) {
      scanf("%d", &a[i][j]);
    }
  }
  double l = 0, c;
  for (i = 0; i < n - 1; i++) {
    l = l + (double)sqrt((a[i][0] - a[i + 1][0]) * (a[i][0] - a[i + 1][0]) +
                         ((a[i][1] - a[i + 1][1]) * (a[i][1] - a[i + 1][1])));
  }
  c = (k * l) / 50;
  printf("%.9lf", c);
  return (0);
}
