int SIZE = 50000001;
int __VERIFIER_nondet_int();
void abort() { };
                                                                                                                                                          
                                                                        
                        
void assume_abort_if_not(int cond) {
  if(!cond) {abort();}
}
/*@ 
    requires ((1 <= \old(cond))) && (cond != 0);
    ensures ((1 <= \old(cond))) && (1);
@*/
void __VERIFIER_assert(int cond) {
  if (!(cond)) {
    ERROR: {/*@ assert(0); */;abort();}
  }
  return;
}
int __VERIFIER_nondet_int();
int main() {
  int n,i,j,k;
  n = __VERIFIER_nondet_int();
  if (!(n <= SIZE)) return 0;
  i = 0; j=0;
/*@
loop invariant ((0 == (i % 2)));
@*/
  while(i<n){ 

    i = i + 4;
    j = i +2;    
  }
  k =i;
/*@
loop invariant (((k % 2) == 0));
@*/
  while( (j%2) == 0){
   j-=4;
   k -=4; 
  }
  __VERIFIER_assert( (k%2) == 0 );
  return 0;
}