#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>

// 可変引数repマクロ https://trap.jp/post/1224/
#define rep1(a) for (long long i = 0; i < (long long)a; i++)
#define rep2(i, a) for (long long i = 0; i < (long long)a; i++)
#define rep3(i, a, b) for (long long i = (long long)a; i <= (long long)b; i++)
#define rep4(i, a, b, c) for (long long i = (long long)a; i <= (long long)b; i += (long long)c)
#define overload4(a, b, c, d, e, ...) e
#define rep(...) overload4(__VA_ARGS__, rep4, rep3, rep2, rep1)(__VA_ARGS__)

#define printYesNo(is_ok) puts(is_ok ? "Possible" : "Impossible")
#define ALL(v) v.begin(), v.end()
#define RALL(v) v.rbegin(), v.rend()
#define SORT(v) sort(ALL(v))
#define RSORT(v) sort(RALL(v))
#define REVERSE(v) reverse(ALL(v))

template <class T>
using pq_asc = priority_queue<T, vector<T>, greater<T>>;
template <class T>
using pq_des = priority_queue<T>;

template <typename T>
void printlnVector(T v)
{
  for (auto n : v)
  {
    cout << n << endl;
  }
}

template <typename T>
void printVector(T v)
{
  for (auto n : v)
  {
    cout << n << " ";
  }
  cout << endl;
}

int main()
{
  string S;
  cin >> S;
  vector<pair<char, int>> dumped_S;
  dumped_S.push_back(pair<char, long long>(S[0], 0));

  for (auto c : S)
  {
    if (dumped_S.back().first != c)
    {
      dumped_S.push_back(pair<char, long long>(c, 0));
    }
    dumped_S.back().second++;
  }

  long long ans = 0;
  rep(i, dumped_S.size() - 1)
  {
    if (dumped_S[i].first == '1' && dumped_S[i].second >= 2 && dumped_S[i + 1].first == '0')
    {
      long long cnt = dumped_S[i].second / 2;
      ans += cnt * dumped_S[i + 1].second;
      swap(dumped_S[i], dumped_S[i + 1]);
      dumped_S[i + 1].second = cnt * 2;
    }
    else if (dumped_S[i].first == '1' && dumped_S[i + 1].first == '1')
    {
      dumped_S[i + 1].second += dumped_S[i].second;
      dumped_S[i].second = 0;
    }
  }

  cout << ans << endl;

  return 0;
}