a.cpp

#include <bits/stdc++.h>

using namespace std;

int main() {
    //freopen("input.txt", "rt", stdin);

    string s; cin >> s;

    {
        string s2 = s;
        s2.erase(unique(s2.begin(), s2.end()), s2.end());

        if (!(s2.size() == 3u && s2[0] == 'a' && s2[1] == 'b' && s2[2] == 'c')) {
            cout << "NO"; return 0;
        }
    }

    int ca = 0, cb = 0, cc = 0;
    for (auto& it : s) {
        ca += it == 'a';
        cb += it == 'b';
        cc += it == 'c';
    }

    if (ca == cc || cb == cc) {
        cout << "YES";
    } else {
        cout << "NO";
    }

    return 0;
}