simple code in c:

int main() {

int t;
scanf("%d",&t);
while (t--) {
 unsigned long long int a;
 scanf("%lld",&a);
  long n = sqrt(2*a);
  if (n*(n+1) == 2*a)    printf("%ld\n",n);
  else printf("-1\n");
}  
return 0;

}