#include<iostream>
#include<cstdio>
#include<cmath> 
#include<cstring>
#include<string>
using namespace std;
const int maxn=100000;
string s;
int v[500];
int main(){
	freopen("xxxx.in","r",stdin);
	freopen("xxxx.out","w",stdout);
	cin>>s;
	int cnt=0;
	for(int i=0;i<s.size();i++)
	  {
	  	if(v[(int)s[i]]==0)
	  	  v[(int)s[i]]=i+1;
	  	  else
	  	   {
			for(int j=v[(int)s[i]]+1;j<=i;j++)
	  	   	  if(v[(int)s[j-1]]!=0) 
	  	   	    cnt++;
	  	   	v[(int)s[i]]=0;
			 }
	  }
        cout<<cnt;
	
}