#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i=0; i<n; i++)

// #include <all.hpp>

#define int long long

signed main() {
  string s;
  cin >> s;
  int n = s.length();
  deque<pair<int, int>> st = {{0, 0}};
  rep(i, n) {
    if(s[i] == '0') {
      if(st.back().first == 0)
        st.back().second++;
      else
        st.emplace_back(0, 1);
    } else {
      if(st.back().first == 1)
        st.back().second++;
      else
        st.emplace_back(1, 1);
    }
  }
  long long ans = 0;
  int one_cnt = 0;
  rep(i, st.size()) {
    if(st[i].first == 0) {
      ans += one_cnt / 2 * st[i].second;
      one_cnt -= one_cnt % 2;
    } else {
      one_cnt += st[i].second;
    }
  }
  cout << ans << endl;
}