// verifast_options{disable_overflow_check target:ILP32}
extern void abort(void);
//@ requires true;
//@ ensures true;
void reach_error()
//@ requires false;
//@ ensures true;
{}
/*
 * Recursive computation of fibonacci numbers.
 * 
 * Author: Matthias Heizmann
 * Date: 2013-07-13
 * 
 */

extern int __VERIFIER_nondet_int(void);
//@ requires true;
//@ ensures true;


int fibonacci(int n) 
//@ requires true;
//@ ensures ((((((((((((8 <= result) && (6 == n)) || (n < 1)) || ((2 == n) && (1 <= result))) || ((4 == n) && (3 <= result))) || ((3 == n) && (2 <= result))) || ((5 == n) && (5 <= result))) || ((7 == n) && (13 <= result))) || ((1 <= result) && (1 == n))) || (33 < result)) || ((21 <= result) && (8 == n))) && (0 <= result));
{    if (n < 1) {
        return 0;
    } else if (n == 1) {
        return 1;
    } else {
        return fibonacci(n-1) + fibonacci(n-2);
    }
}


int main() 
//@ requires module(Fibonacci03__verifast_instrumented, true);
//@ ensures junk();
{
    //@ open_module(); 
    int x = __VERIFIER_nondet_int();
    if (x > 46) {
        return 0;
    }
    int result = fibonacci(x);
    if (x < 9 || result >= 34) {
        return 0;
    } else {
        ERROR: {reach_error();abort();}
    }
 return 0; }