void abort() { };

                                                                       
                                                  
                                                                             
                                                                   
                                                  
                                                                             
                                                                              
                                                                             

                                                                                                                                                               
                        
void assume_abort_if_not(int cond) {
  if(!cond) {abort();}
}
/*@ 
    requires ((cond != 0)) && (cond != 0);
    ensures ((cond != 0)) && (1);
@*/
void __VERIFIER_assert(int cond) {
  if (!(cond)) {
      ERROR: {/*@ assert(0); */;abort();}
  }
  return;
}
int __VERIFIER_nondet_int();
int main() {
    int i, n, a, b;
    i = 0; a = 0; b = 0; n = __VERIFIER_nondet_int();
    if(!(n >= 0 && n <= 1000000)) return 0;
/*@
loop invariant (((((long long) b + a) <= ((long long) n * 3)) && (((long long) b + a) == ((long long) i * 3))));
@*/
    while (i < n) {
        if (__VERIFIER_nondet_int()) {
            a = a + 1;
            b = b + 2;
        } else {
            a = a + 2;
            b = b + 1;
        }
        i = i + 1;
    }
    __VERIFIER_assert(a + b == 3*n);
    return 0;
}