/*
Alphabet
SER 2016
by Dennis Matveyev

How:  Standard LIS 
Complexity:  O(n log n)
*/

#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
using namespace std;

int L(string s)
{
	vector<char>::iterator low;
	vector<char> v;

	for each (char c in s)
	{
		low = lower_bound(v.begin(), v.end(), c);
		if (low == v.end())
			v.push_back(c);
		else
			*low = c;
	}

	return v.size();
}

int main()
{
	//harcoded for testing
	string s = "abcdefghijklmnopqrstuvw";
	cout << 26 - L(s) << endl;

	return 0;
}