// verifast_options{disable_overflow_check target:ILP32}
extern void abort(void);
//@ requires true;
//@ ensures true;


void reach_error()
//@ requires false;
//@ ensures true;
{}void assume_abort_if_not(int cond) 
//@ requires true;
//@ ensures true;
{  if(!cond) {abort();}
}
void __VERIFIER_assert(int cond) 
//@ requires (cond != 0);
//@ ensures (cond != 0);
{  if (!(cond)) {
  ERROR: {reach_error();abort();}
  }
  return;
}
int __VERIFIER_nondet_int();
//@ requires true;
//@ ensures true;
int main() 
//@ requires module(half__verifast_instrumented, true);
//@ ensures junk();
{
    //@ open_module(); 
    int i = 0;
    int n = 0;
    int k = __VERIFIER_nondet_int();
    if (!(k <= 1000000 && k >= -1000000)) return 0;
for(i = 0; i < 2*k; i++)
//@ invariant (((((n * 2) == (i + 1)) && (n <= k)) || ((n == 0) && (i == 0))) || ((i == (n * 2)) && (n <= k)));
    {
 if (i % 2 == 0) {
     n ++;
 }
    }
    __VERIFIER_assert(k < 0 || n == k);
    return 0;
}