#include<iostream>

#include<cstring>

#include<cstdio>

#include<algorithm>

using namespace std;

char s[];

int main()

{

    int cnt = ;

    char now = 'a';

    scanf("%s",s);

    int len = strlen(s);

    for(int i = ;i < len;i++)

    {

        if(now <= s[i])    cnt += min(s[i]-now,now+-s[i]);

        else    cnt += min(now-s[i],s[i]+-now);

        now = s[i];

    }

    printf("%d\n",cnt);

    return ;

}