void abort() { };
                                                                                                                                                          
                                                                              

/*
 * Recursive implementation integer addition.
 * 
 * Author: Matthias Heizmann
 * Date: 2013-07-13
 * 
 */

extern int __VERIFIER_nondet_int();

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


int main() {
    int m = __VERIFIER_nondet_int();
    if (m < 0 || m > 1073741823) {
        // additional branch to avoid undefined behavior 
        // (because of signed integer overflow)
        return 0;
    }
    int n = __VERIFIER_nondet_int();
    if (n < 0 || n > 1073741823) {
        // additional branch to avoid undefined behavior 
        // (because of signed integer overflow)
        return 0;
    }
    int result = addition(m,n);
    if (result == m + n) {
        return 0;
    } else {
        ERROR: {/*@ assert(0); */;abort();}
    }
}