CUBE-158: Square Prime

#include <bits/stdc++.h>
using namespace std;
vector <bool> prime(1e3+1,true);
int main(){

    int a,b;
    scanf("%d%d",&a,&b);

    set <int> square_prime;
    prime[0] = false;
    prime[1] = false;
    for(int i=2;i<=1e3;i++){
        if(prime[i] == true){
            square_prime.insert(i*i);
            for(int j=i+i;j<=1e3;j=j+i){
                prime[j] = false;
            }
        }
    }

    bool found = false;
    for(int i=a;i<=b;i++){
        if(square_prime.find(i) != square_prime.end()) {
            printf("%d ",i);
            found = true;
        }
    }
    if(!found) printf("-1");

    return 0;
}