alphabet.cpp

// Michael Pfeifer
// Version 04, 2018/02/17

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

typedef long long ll;
typedef long double ld;
typedef unsigned int uint;
typedef unsigned long long ull;

const ld  pi   = 4.0*atanl(1.0);
const int iinf = 1e9 + 10;
const ll  inf  = 1e18 + 10;
const int mod  = 1000000007;
const ld  prec = .000001;

#define enld endl
#define endl '\n'
#define pb push_back
#define debug(x) cout<<#x<<" -> "<<x<<'\n'
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define uni(x) (x).erase(unique(all(x)), (x).end())
#define rep(i, n) for (ll i = 0; i < (ll)(n); ++i)
#define rep1(i, n) for (ll i = 1; i <= (ll)(n); ++i)
#define umap unordered_map
#define uset unordered_set

template<class TIn>
using indexed_set = tree<
        TIn, null_type, less<TIn>,
        rb_tree_tag, tree_order_statistics_node_update>;

void fast() {
    ios::sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);
}

void file() {
    auto a = freopen("a.in",  "r", stdin);
    auto b = freopen("a.out", "w", stdout);
    if(!a || !b) cout << "uh oh" << endl;
}





int main() {
    //file();
    //fast();

    string s;
    cin >> s;
    s = "?" + s;

    string t = "abcdefghijklmnopqrstuvwxyz";
    t = "*" + t;

    vector<vector<int>> v;
    v.resize(s.size(), vector<int>(t.size(), 0));

    for(int i = 0; i < s.size(); i++) {
        for(int j = 0; j < t.size(); j++) {
            if(i > 0 && j > 0 && s[i] == t[j]) {
                v[i][j] = v[i-1][j-1] + 1;
            }
            if(i > 0) {
                v[i][j] = max(v[i][j], v[i-1][j]);
            }
            if(j > 0) {
                v[i][j] = max(v[i][j], v[i][j-1]);
            }
        }
    }

    int lis = v[s.size()-1][t.size()-1];
    cout << 26 - lis << endl;

    return 0;
}