#include <stdio.h>
#include <math.h>

long state = 11;
long lcg() {
  state = (1103515245L * state + 12345L) % 2147483648L;
  return state;
}
double uniform() { return (double)lcg() / 2147483648.0; }
double exponential(double rate) {
  double u = uniform();
  if (u < 1e-12) u = 1e-12;
  return -log(u) / rate;
}

int main() {
  double lambda = 4.0, mu = 5.0;
  double t = 0.0;
  double nextArrival = exponential(lambda);
  double nextDeparture = -1.0;
  int queue = 0, served = 0;
  double totalWait = 0, busyTime = 0;
  while (served < 1000) {
    if (nextArrival < nextDeparture || nextDeparture < 0) {
      t = nextArrival;
      if (queue == 0) nextDeparture = t + exponential(mu);
      queue++;
      nextArrival = t + exponential(lambda);
    } else {
      t = nextDeparture;
      queue--;
      served++;
      totalWait += t;
      if (queue > 0) {
        nextDeparture = t + exponential(mu);
      } else {
        nextDeparture = -1;
      }
    }
  }
  busyTime = t;
  printf("served        = %d\n", served);
  printf("utilization   = %.3f (rho = 0.8)\n", busyTime > 0 ? 1.0 : 0.0);
  printf("avg wait      = %.3f\n", totalWait / served);
  return 0;
}