求助

#include<stdio.h>
#include <string.h>
int main(){
    int n,cnt=0;
    scanf("%d",&n);
    int prime[n],ans[n];
    memset(prime,-1,sizeof(prime));
    memset(ans,-1,sizeof(ans));
    for (int i = 2; i <= n; ++i) {
        if(prime[i]){
            for (int j = 2; j*i <= n; ++j) {
                prime[i*j]=0;
            }
        }
    }
    for (int i = 4; i <= n; ++i) {
        if(prime[i]&&prime[i-2]){
            printf("%d %d\n",i-2,i);
            cnt=1;
        }
        }
    if(cnt==0)
        printf("empty");
    return 0;
}