void abort() { };

                                                                       
                                                  
                                                                             
                                                                   
                                                  
                                                                             
                                                                              
                                                                             

                                                                                                                                                               
                        
void assume_abort_if_not(int cond) {
  if(!cond) {abort();}
}
/*@ 
    requires ((1 <= cond)) && (cond != 0);
    ensures ((1 <= cond)) && (1);
@*/
void __VERIFIER_assert(int cond) {
  if (!(cond)) {
      ERROR: {/*@ assert(0); */;abort();}
  }
  return;
}
int __VERIFIER_nondet_int();
int main() {
    int lo, mid, hi;
    lo = 0;
    mid = __VERIFIER_nondet_int();
    if (!(mid > 0 && mid <= 1000000)) return 0;
    hi = 2*mid;
/*@
loop invariant ((((lo + ((long long) mid * 2)) == hi) && (lo <= hi)));
@*/
    while (mid > 0) {
        lo = lo + 1;
        hi = hi - 1;
        mid = mid - 1;
    }
    __VERIFIER_assert(lo == hi);
    return 0;
}