void abort() { };
                                                                                                                                                          
                                                                           

/*@ 
    requires (1);
    ensures ((((((\result == ((long long) 2 + m)) && (2 == n)) || ((\result <= m) && (((long long) n + m) <= \result))) || ((\result == ((long long) m + 1)) && (n == 1))) || (2 < n)));
@*/
int sum(int n, int m) {
    if (n <= 0) {
      return m + n;
    } else {
      return sum(n - 1, m + 1);
    }
}

int main() {
  int a = 2;
  int b = 3;
  int result = sum(a, b);
  if (result != a + b) {
    ERROR: {/*@ assert(0); */;abort();}
  }
}