#include <iostream>
#include <iomanip>//小数点出力用
//cout << fixed << setprecision(10) << ans;
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <set>
#include <map>
using ll = long long;
using namespace std;
#define modP 998244353
bool chkrng0idx(int pos, int sup) { return (0 <= pos && pos < sup); }
int clk4(int num) { return (num - 2) * (num % 2); }
void yn(bool tf) { cout << (tf ? "Yes\n" : "No\n"); }

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    string S;cin >> S;
    ll ans = 0;
    int point = 0;
    int combo1 = 0;
    for (int i = S.size() - 1;i >= 0;i--) {
        if (S[i] == '0') {
            point++;
            combo1 = 0;
        }
        else {
            combo1++;
            if (combo1 == 2) {
                ans += (ll)point;
                combo1 = 0;
            }
        }
    }
    cout << ans;
    return 0;
}