#include<iostream>
#include<cstring>
#include<vector>
using namespace std;
const int N=1e6+10,INF=-1e9;
char s[N];
int f[N][2];
int n;
int main(){
cin>>s+1;int res=0;
n=strlen(s+1);
f[0][0]=0;f[0][1]=INF;
for(int i=1;i<=n;i++){
f[i][1]=f[i-1][0]+s[i]-'a'+1;
f[i][0]=max(f[i-1][0],f[i-1][1]);
}
res=max(f[n][0],f[n][1]);
cout<<res<<endl;
return 0;
}