#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i, n) for (long long i = 0; i < (long long)(n); i++)
template <typename T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template <typename T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }

int main() {
    string S;
    cin >> S;

    reverse(S.begin(),S.end());

    long long movedNum = 0;
    long long wall = -1;
    long long state_one = 0;
    long long res = 0;
    rep(i,S.size()){
        if(state_one == 0){
            if(S[i] == '1'){
                state_one = 1;
            }
        }else{
            state_one = 0;
            if(S[i] == '0'){
                // wall = i - 1;
                movedNum = 0;
            }else{
                res += i-wall-2-2*movedNum;
                movedNum++;
            }
        }
    }

    cout << res << endl;
}