#include<iostream>
#include<cstring>
#include<cmath>
using namespace std;

int main()
{
   char a[100000];  cin>>a;
   long long sum=1e7;
   for(char j='a';j<='z';j++)
   {
     int count=0;
     for(int i=0;i<strlen(a);i++)
   {
      int diff=abs(a[i]-j);
      count+=min(diff,26-diff);
   }
    if(count<sum)  sum=count;
   }
   cout<<sum;
}