10948 - The primary problem solutions

#include<cstdio>
#include<iostream>
#include<cstring>
#include<cmath>

using namespace std;
int main()
{
    long i,j,k;
    long n=1000010;
    bool prime[n];
    memset(prime,true,sizeof prime);
    for(i=2; i<=sqrt(n); i++)
    {
        if(prime[i]==true)
        {
            for(j=i*i; j<=n; j+=i)
                prime[j]=false;
        }
    }
    long num;
    while(scanf("%d",&num)==1 && num)
    {
        int c=1;
        printf("%ld:\n",num);
        if(prime[num-2])
        {
            c=0;
            printf("2+%ld\n",num-2);
        }
        else
        {

            for(i=3; i<=num/2; i+=2)
            {
                if(prime[i] && prime[num-i])
                {
                    printf("%ld+%ld\n",i,num-i);
                    c=0;
                    break;
                }
            }
        }
        if(c)
            printf("NO WAY!\n");
    }
    return 0;
}