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

int main(){
    string S;
    getline(cin, S);
    int cnt[300] = {0};
    for(char c : S) cnt[c]++;
    int N = S.size();
    for(int i=0; i<N; i++) for(int j=i; j<N-1; j+=2){
        map<char, int> mp;
        for(int k=i; k<=j; k+=2) mp[S[k]]++;
        bool ok = true;
        for(auto& p : mp) if(p.first == ' ' || cnt[p.first] != p.second) ok = false;
        if(ok){
            cout << "Yes" << endl;
            return 0;
        }
    }
    cout << "NO" << endl;
    return 0;
}