// Arup Guha
// 11/5/2016
// Solution to SER 2016 Division I Problem A: Alphabet

import java.util.*;

public class alphabet {

	public static void main(String[] args) {

		// Read in string.
		Scanner stdin = new Scanner(System.in);
		String s = stdin.next();

		// Set up LIS DP.
		int[] lis = new int[s.length()];
		Arrays.fill(lis, 1);

		// Run it.
		for (int i=1; i<lis.length; i++)
			for (int j=0; j<i; j++)
				if (s.charAt(i) > s.charAt(j))
					lis[i] = Math.max(lis[i], lis[j]+1);

		// Find best answer.
		int res = lis[0];
		for (int i=1; i<lis.length; i++)
			res = Math.max(res, lis[i]);

		// Output (difference from 26...)
		System.out.println(26-res);
	}
}