extern int __VERIFIER_nondet_int(); int rec1(int i); int rec2(int j); int rec1(int i) { if(i <= 0) return 0; return rec2(rec1(i+1)); } int rec2(int j) { if(j <= 0) return 0; return rec1(rec2(j-1)); } int main() { int x = __VERIFIER_nondet_int(); rec2(x); }