#include <iostream>
#include <string>
#include <set>

using namespace std;

int main() {
    string S;
    cin >> S;

    set<char> unique_chars;
    for (char c : S) {
        unique_chars.insert(c);
    }

    if (unique_chars.size() == 2) {
        cout << "Yes" << endl;
    } else {
        cout << "No" << endl;
    }

    return 0;
}