#include <stdio.h>


int f(int r0) {
	int r2 = 1;
	int r1 = 1;
back16:
	r2 = r2 * r0;
	r0 = r0 - r1;
	if (r0 > r1) {
		goto back16;
	}
	return r2;
}

int main() {
	int vals[] = {2, 3, 4, 9};
	for (int i=0; i<4; i++) {
		printf("f( r0=%d ) = %d\n", vals[i], f(vals[i]));
	}
	return 0;
}