// verifast_options{disable_overflow_check target:ILP32}
extern void abort(void);
//@ requires integer(&counter, ?veri_req_counter) &*& true;
//@ ensures integer(&counter, ?veri_ens_counter) &*& true;
void reach_error()
//@ requires false;
//@ ensures true;
{}extern int __VERIFIER_nondet_int(void);
//@ requires integer(&counter, ?veri_req_counter) &*& true;
//@ ensures integer(&counter, ?veri_ens_counter) &*& true;
void assume_abort_if_not(int cond) 
//@ requires integer(&counter, ?veri_req_counter) &*& true;
//@ ensures integer(&counter, ?veri_ens_counter) &*& true;
{  if(!cond) {abort();}
}
void __VERIFIER_assert(int cond) 
//@ requires integer(&counter, ?veri_req_counter) &*& (1 <= cond);
//@ ensures integer(&counter, ?veri_ens_counter) &*& (1 <= cond);
{    if (!(cond)) {
    ERROR:
        {reach_error();}
    }
    return;
}

int counter = 0;
int main() 
//@ requires module(ps2_ll_unwindbound50__verifast_instrumented, true) &*& (counter == 0);
//@ ensures (counter == 0) &*& junk();
{
    //@ open_module(); 
    int k;
    long long y, x, c;
    k = __VERIFIER_nondet_int();

    y = 0;
    x = 0;
    c = 0;

while (counter++<50)
//@ invariant integer(&counter, ?veri_inv_counter) &*& (((x * 2) == (y + (y * y))) && (veri_req_counter == 0));
    {
        __VERIFIER_assert((y * y) - 2 * x + y == 0);

        if (!(c < k))
            break;

        c = c + 1;
        y = y + 1;
        x = y + x;
    }
    __VERIFIER_assert((y*y) - 2*x + y == 0);
     
    return 0;
}