#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int i = 0; i< (n); ++i)
#define repi(i, a, b) for (int i = (a); i < (b); ++i)
#define all(x) (x).begin(), (x).end()
#define fore(i, a) for(auto &i:a)
using ll = long long;

int main() {
	string s;
	cin >> s;
	ll one = 0;
	ll two = 0;
	ll idx = s.size()-1;
	ll ans = 0;
	ll n = s.size();
	while(idx >= 0){
		if(idx == 0){
			break;
		}
		if(s[idx] == '1' && s[idx-1] == '1'){
      ans += n-1-idx-one-2*two;
			two++;
			idx-=2;
		}
		if(s[idx] == '1' && s[idx-1] == '0'){
			one++;
			idx-=2;
		}
		if(s[idx] == '0'){
			idx--;
		}
	}
	cout << ans << endl;
}