#include<bits/stdc++.h>
#define For(i, a, b) for (int i = (a); i <= (b); ++i)
#define Rof(i, a, b) for (int i = (a); i >= (b); --i)
using namespace std;
using i64 = long long;
constexpr int _N = 1e6 + 5;
string c;
deque<pair<int, int>> q;
int cnt[26];
signed main() {
	ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	cin >> c;
	int n = c.length() / 2;
	for (char t : c) ++cnt[t - 'a'];
	For(i, 0, 25) if (cnt[i])
		q.push_back({ i, cnt[i] });
	string ans;
	while (!q.empty()) {
		auto cur = q.front(); q.pop_front();
		int cnt = min(n, cur.second);
		For(i, 1, cnt)
			ans += cur.first + 'a', --cur.second;
		if (cur.second) q.push_back(cur);
	}
	if (ans.front() == ans.back()) cout << "NO\n";
	else cout << "YES\n" << ans << '\n';
}