#include <bits/stdc++.h>
double dist(double x, double x2, double y, double y2) {
  return sqrt((x - x2) * (x - x2) + (y - y2) * (y - y2));
}
int main(void) {
  int n, k, i;
  double sumlen = 0;
  double Ax, Ay, Apx = 0, Apy = 0;
  scanf("%d %d", &n, &k);
  for (i = 0; i < n; ++i) {
    scanf("%lf %lf", &Ax, &Ay);
    if (i > 0) sumlen += dist(Ax, Apx, Ay, Apy);
    Apx = Ax;
    Apy = Ay;
  }
  printf("%.9lf", sumlen * k / 50.00);
  return 0;
}
