Codeforces 1073A——防自闭

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#include <bits/stdc++.h>
using namespace std;
const int maxn = 1010;
int n;
char s[maxn];
int cnt[26];
int main() {
    scanf("%d", &n);
    scanf("%s", s);
    bool ans = false;
    for (int i = 0; i < n; i++) {
        memset(cnt, 0, sizeof(cnt));
        bool flag = false;
        for (int j = i; j < n; j++) {
            cnt[s[j]-'a']++;
            int len = (j - i + 1)/2;
            bool ok = true;
            for (int k = 0; k < 26; k++) {
                if (cnt[k] > len) {
                    ok = false;
                    break;
                }
            }
            if (ok) {
                printf("YES\n");
                for (int k = i; k <= j; k++) {
                    printf("%c", s[k]);
                }
                printf("\n");
                flag = true;
                break;
            }
        }
        if (flag) {
            ans = true;
            break;
        }
    }
    if (!ans) printf("NO\n");
    return 0;
}