#include<bits/stdc++.h>
using namespace std;
char a[100005];
bool z[30],bjj[100005];
int bj[30];

void run(){
	int ans=0;
	for(int i=0;i<strlen(a);i++){
		int d=a[i]-'a'+1;
		if(z[d]){
			for(int j=bj[d]+1;j<=i-1;j++){
				if(bjj[j]) ans++;
			}
			bjj[i]=0,bjj[bj[d]]=0,z[d]=0;
		}
		else{
			z[d]=1;bj[d]=i;bjj[i]=1;
		}
	}
	
	printf("%d",ans);
}
int main(){
	freopen("xxxx.in","r",stdin);
    freopen("xxxx.out","w",stdout);
    scanf("%s",a);
    
    run();
	return 0;
}