uva : 543 - Goldbach's Conjecture

#include<stdio.h>
#include<math.h>
int main()
{
    long num;
    while(scanf("%ld",&num)==1)
    {
        if(num==0)
          break;
        long i,j,k,l,m=0,n=0,nn=0;
        for(i=2;i<=(num/2)+1;i++)
        {
            n=0;
            for(j=2;j<=sqrt(i);j++)
            {
                if(i%j==0)
                    n++;
            }
            if(n==0)
            {
                m=num-i;k=0;
                for(j=2;j<=sqrt(m);j++)
                {
                    if(m%j==0)
                    {
                        k++;
                    }
                }
                if(k==0)
                  {
                      nn=1;
                      break;
                  }
            }
        }
        if(nn==0)
        {
            printf("Goldbach's conjecture is wrong.\n");
        }
        else
        {
            printf("%ld = %ld + %ld\n",num,i,m);
        }
    }
    return 0;
}