#include <stdio.h>
#include <assert.h>

static int add(int x, int y) {
    return x+y;
}

int main()
{
    int a = 10;
    int sum = add(a++, a++);
    printf("This should be 21: %d\n", sum);
    printf("a should be 12: %d\n", a);
    assert(sum == 21);
    assert(a == 12);
    return 0;
}