#include <stdio.h>
int multiply(int x, int y) {
if (y > 0) {
return (x + multiply(x, y - 1));
}
if (y < 0) {
return -multiply(x, -y);
}
return 0;
}
int main()
{
printf("%d\n", multiply(3, 7));
printf("%d\n", multiply(4, 16));
printf("%d\n", multiply(5, 0));
printf("%d\n", multiply(0, 8));
printf("%d\n", multiply(2, -5));
printf("%d\n", multiply(-4, 6));
printf("%d\n", multiply(-5, -7));
return 0;
}
/*
run:
21
64
0
0
-10
-24
35
*/