UVA-Goldbach's Conjecture

#include<bits/stdc++.h>
using namespace std;
#define fastread()(ios_base::sync_with_stdio(false),cin.tie(NULL));
vector<bool>is_prime(1000000,true);
int main()
{
    int i,j,n;
    for(i=2; i<=sqrt(1000000); i++)
    {
        if(is_prime[i])
        {
            for(j=i*i; j<=1000000; j+=i)
                is_prime[j]=false;
        }
    }

    while(scanf("%d",&n))
    {
        if(n==0)
            break;


        for(i=3; i<n/2+1; i+=2)
        {
            if(is_prime[i])
            {
                if(is_prime[n-i])
                {
                    printf("%d = %d + %d\n",n,i,n-i);
                    break;
                }
            }
        }
        if(i>n/2+1)
            printf("Goldbach's conjecture is wrong.\n");

    }
    return 0;
}