void abort() { };
                                                                                                                                                          
                                                                              

/*
 * recHanoi.c
 *
 *  Created on: 17.07.2013
 *      Author: Stefan Wissert
 */

extern int __VERIFIER_nondet_int();

/*
 * This function returns the optimal amount of steps,
 * needed to solve the problem for n-disks
 */
/*@ 
    requires (1);
    ensures ((((((((3 <= \result) && (n <= 2)) || (126 < \result)) || ((((long long) n + 11) <= \result) && (31 <= \result))) || ((\result == 1) && (n == 1))) || ((7 <= \result) && (n <= 3))) || ((15 <= \result) && (n <= 4))));
@*/
int hanoi(int n) {
    if (n == 1) {
		return 1;
	}
	return 2 * (hanoi(n-1)) + 1;
}


int main() {
    int n = __VERIFIER_nondet_int();
    if (n < 1 || n > 31) {
    	return 0;
    }
    int result = hanoi(n);
    if (result >= n) {
        return 0;
    } else {
        ERROR: {/*@ assert(0); */;abort();}
    }
}