Alphabet

    1#include <bits/stdc++.h>
    2using namespace std;
    3using ll = long long;
    4using i128 = __int128;
    5const int inf = 1e9;
    6const ll INF = 1e18; //❄️
    7int main() {
    8    ios::sync_with_stdio(0); cin.tie(0); 
    9    string s; cin >> s;
    10    vector<int> ans;
    11    for (int i = 0; i < s.size(); i++) {
    12        if (ans.empty() || s[i] - 'a'> ans.back()) {
    13            ans.push_back(s[i] - 'a');
    14        } else {
    15            int pos = lower_bound(ans.begin(), ans.end(), s[i] - 'a') - ans.begin();
    16            ans[pos] = s[i] - 'a';
    17        }
    18    }
    19    cout << 26 - ans.size() << '\n';
    20    return 0;
    21}