// 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();
int main() 
//@ requires module(bhmr2007__verifast_instrumented, true);
//@ ensures junk();
{
    //@ open_module(); 
    int i, n, a, b;
    i = 0; a = 0; b = 0; n = __VERIFIER_nondet_int();
    if(!(n >= 0 && n <= 1000000)) return 0;
while (i < n)
//@ invariant (((b + a) <= (n * 3)) && ((b + a) == (i * 3)));
    {
if (__VERIFIER_nondet_int()) 
//@ requires true;
//@ ensures true;
{            a = a + 1;
            b = b + 2;
        } else {
            a = a + 2;
            b = b + 1;
        }
        i = i + 1;
    }
    __VERIFIER_assert(a + b == 3*n);
    return 0;
}