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

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    string S;
    cin >> S;

    using Key = tuple<int,int,int,int>;
    map<Key,int> dp;
    dp[{0,0,0,0}] = 0;

    auto in_range = [&](const Key& t){
        return 0 <= get<0>(t) && get<0>(t) <= 20 &&
               0 <= get<1>(t) && get<1>(t) <= 20 &&
               0 <= get<2>(t) && get<2>(t) <= 20 &&
               0 <= get<3>(t) && get<3>(t) <= 20;
    };

    for (char c : S) {
        map<Key,int> pp = dp;  // pp = dp.copy()
        dp = pp;               // dp, pp = pp, dp  ←「何もしない」遷移も維持

        for (auto const& it : pp) {
            const Key& key = it.first;
            auto [k,u,r,o] = key;
            int val = it.second;

            auto push = [&](Key nk, int v){
                if (in_range(nk)) {
                    dp[nk] = max(dp[nk], v);
                }
            };

            Key nkey;
            bool has_nkey = true;

            // --- match c ---
            if (c == 'K') {
                nkey = {k+1, u, r, o};
            } else if (c == 'U') {
                nkey = {k-1, u+1, r, o};
            } else if (c == 'R') {
                nkey = {k, u-1, r+1, o};
            } else if (c == 'O') {
                nkey = {k, u, r-1, o+1};
            } else if (c == 'I') {
                has_nkey = false;
                if (o > 0) {
                    push({k, u, r, o-1}, val + 1);
                }
            } else {
                has_nkey = false;
            }

            // normal transitions (non-I)
            if (has_nkey) {
                if (in_range(nkey)) {
                    push(nkey, val);
                }
            }

            // --- '?' case ---
            if (c == '?') {
                vector<Key> nkeys = {
                    {k+1, u,   r,   o},
                    {k-1, u+1, r,   o},
                    {k,   u-1, r+1, o},
                    {k,   u,   r-1, o+1},
                };
                for (auto &nk : nkeys) {
                    if (in_range(nk)) push(nk, val);
                }

                if (o > 0) {
                    push({k, u, r, o-1}, val + 1);
                }
            }
        }
    }

    int ans = 0;
    for (auto &it : dp) ans = max(ans, it.second);

    cout << ans << "\n";
    return 0;
}