思路：

　　筛法筛出素数，逐个判断即可。

#include
     
      #include
      
       #include
       
        using namespace std;const int maxn = 1000010;int cnt, a;int prime[maxn];int isnprime[maxn];void findpri(int lim){    for(int i = 2; i <= lim; ++i){        if(!isnprime[i])            prime[++cnt] = i;        for(int j = 1; j <= cnt; ++j){            if(i * prime[j] > lim)    break;            isnprime[i * prime[j]] = 1;            if(i % prime[j] == 0)        break;        }    }}int main(void) {    findpri(maxn - 10);    while(scanf("%d", &a) && a){        for(int i = 1; i <= cnt; ++i){            if(!isnprime[a - prime[i]]){                printf("%d = %d + %d\n", a, prime[i], a - prime[i]);                break;            }        }    }    return 0;}