#include "bits/stdc++.h"
#define intt long long
#define pb push_back
#define endl '\n'
#define F first
#define S second
#define pii pair<int,int>
#define pll pair<intt,intt>
#define ld long double
using namespace std;
int i,j;
int main(){
string s;
cin >> s;
int n = s.size();
if ( n%2 == 0 ){
cout << 1.0*n/4*(n/2-1) << endl;
}
else{
cout << 1.0*(n-1)/4*(n-1)/2 << endl;
}
// ld res = 0;
// for ( i = 1; i <= (n+1)/2; i++ ) res += 1.0*(i-1)/2;
// for ( ; i <= n; i++ ) res += 1.0*(n-i)/2;
// cout << res << endl;
}
