random number generation

// re4(8).cpp
/* this program generates a random number from a set of given numbers, 20 times */
#include<iostream>
#include<stdlib.h>
#include<strings.h>

using namespace std;

int main()
{
    int numbers[] = { 3, 13, 22, 57, 417 };
    int length = sizeof(numbers);
    for (int aa=1;aa<=20;aa++)
        {cout <<numbers[rand()%length]<< endl;}
}