#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
int main () {
char s[100010];
scanf("%s",s);
int len=strlen(s);
int cnt[26]={0}; //计算串内每个字母的数量
for(int i=0;i<len;i++){
cnt[ s[i]-'a' ]++;
}
//极大值最小操作次数
int min_sum = 100010;
for(int target=0;target<26;target++){ //遍历移动到每个字母次数
int total=0;
for(int c=0;c<26;c++){ //当前字母
if(cnt[c]==0){
continue;
}
int diff = abs(target - c);
int min = (diff>(26-diff))?(26-diff):diff;
total += min * cnt[c];
}
if(total<min_sum){
min_sum = total;
}
}
printf("%d",min_sum);
}