#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    string s;
    cin >> s;
    ll a = 0, b = 0, c = 0, flg = 0;
    for (int i = 0; i < (int)s.size(); i++)
    {

        if (s[i] == 'A')
        {
            a++;
        }

        if (s[i] == 'B')
        {
            b++;
        }

        if (s[i] == 'C')
        {
            c++;
        }

        if (a >= 1 && b >= 1 && c >= 1)
        {
            a--;
            b--;
            c--;
        }

        flg = max(max(flg, a), max(b, c));
    }

    cout << flg << "\n";

    return 0;
}