#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;

    for (char c : S) {
        map<Key,int> pp = dp;  // copy
        dp.clear();

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

            Key nkey;
            bool has = true;

            auto push = [&](Key nk, int v){
                if (get<0>(nk) >= 0 && get<1>(nk) >= 0 && get<2>(nk) >= 0 && get<3>(nk) >= 0) {
                    dp[nk] = max(dp[nk], v);
                }
            };

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

            // ---- c == '?' の場合、4 方向全部試す + 'I' も試す ----
            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) {
                    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;
}