Codeforces #270 A. Design Tutorial: Learn from Math（数论：素数判断）

#include <bits/stdc++.h>
using namespace std;

bool judge(int x) {
for(int i=2; i*i<=x; ++i) {
if(x % i == 0)
return true;
}
return false;
}

int main(void) {
int n;
scanf("%d", &n);
for(int i=4; i<n; ++i) {
if(judge(i) && judge(n-i)) {
printf("%d %d\n", i, n-i);
break;
}
}
return 0;
}