Prime Character

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int prime[2002] = {0};
    int i, j, C = 0, t;
    prime[0] = prime[1] = 1;
    for(i = 2; i < 2002; i++)
        if(prime[i] == 0) {
            for(j = 2; i*j < 2002; j++)
                prime[i*j] = 1;
        }
    char s[2002];
    scanf("%d", &t);
    while(t--) {
        scanf("%s", s);
        int asci[128] = {0};
        for(i = 0; s[i]; i++)
            asci[s[i]]++;
        printf("Case %d: ", ++C);
        for(i = 0, j = 0; i < 128; i++)
            if(prime[asci[i]] == 0)
                printf("%c", i), j++;
        if(j == 0)    printf("empty");
        puts("");
    }
    return 0;
}