#include <iostream>
#include <vector>

using namespace std;

int main() {
    string s;
    getline(cin, s);

    bool ret = false;
    for (int i = 0; i < s.size(); i++) {
        for (int j = i + 2; j <= s.size(); j++) {
            bool ok = true;
            vector<int> x(26);
            for (int k = 0; k < s.size(); k++) {
                if (i <= k && k < j && (k - i) % 2 == 0) {
                    if (!isalpha(s[k]))ok = false;
                    else {
                        if (x[s[k] - 'a'] == -1)ok = false;
                        x[s[k] - 'a'] = 1;
                    }
                } else if (isalpha(s[k])) {
                    if (x[s[k] - 'a'] == 1)ok = false;
                    x[s[k] - 'a'] = -1;
                }
            }
            if (ok) ret = true;
        }
    }

    cout << (ret ? "Yes" : "NO") << endl;
    return 0;
}