void abort() { };
                                                                       
                                                  
                                                                             
                                                                   
                                                  
                                                                             
                                                                              
                                                                             

                                                                                                                                                                                  
extern int __VERIFIER_nondet_int();
extern _Bool __VERIFIER_nondet_bool();
/*@ 
    requires ((cond != 0)) && (cond != 0);
    ensures ((cond != 0)) && (1);
@*/
void __VERIFIER_assert(int cond) {
  if (!cond) {
    /*@ assert(0); */;
  }
}
int main() {
  int i = __VERIFIER_nondet_int();
  int n = __VERIFIER_nondet_int();
  int sum = __VERIFIER_nondet_int();
  if (!(i==0 && n>=0 && n<=100 && sum==0)) return 0;
/*@
loop invariant (((0 <= i) && (0 <= sum)));
@*/
  while (i<n) {
    sum = sum + i;
    i++;
  }
  __VERIFIER_assert(sum>=0);
  return 0;
}