int SIZE = 50000001;
void abort() { };

int __VERIFIER_nondet_int();
                        
                                                                                                                                                          
                                                                        
                        
void assume_abort_if_not(int cond) {
  if(!cond) {abort();}
}
/*@ 
    requires ((cond != 0)) && (cond != 0);
    ensures (((cond != 0) && (SIZE == \old(SIZE)))) && (1);
@*/
void __VERIFIER_assert(int cond) {
  if (!(cond)) {
    ERROR: {/*@ assert(0); */;abort();}
  }
  return;
}


/*@ 
    requires (1);
    ensures ((SIZE == \old(SIZE)));
@*/
int main() {
  int n,i,j;
  n = __VERIFIER_nondet_int();
  if (!(n <= SIZE)) return 0;
  i = 0; j=0;
/*@
loop invariant ((((i >= 0) ? (i % 3) : ((i % 3) + 3)) == 0));
@*/
  while(i<n){ 
 
    if(__VERIFIER_nondet_int())	  
      i = i + 6; 
    else
     i = i + 3;    
  }
  __VERIFIER_assert( (i%3) == 0 );
  return 0;
}