/*
 * Program from Ex.1 of
 * 2001POPL - Lee,Jones,Ben-Amram - The size-change principle for program termination
 * where we abstracted lists by their size.
 *
 * Date: 12.12.2013
 * Author: heizmann@informatik.uni-freiburg.de
 *
 */

extern int __VERIFIER_nondet_int(void);

int r1(int ls, int a) {
	if (ls == 0) {
		return a;
	} else {
		return r1(ls-1, ls+1+a);
	}
}

int rev(int ls) {
	return r1(ls,0);
}

int main() {
	int ls = __VERIFIER_nondet_int();
	if ( ls >= 0) {
		rev(ls);
	}
	return 0;
}