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

int main() {
  string S; cin >> S;
  int N = S.size(), zero = 0, C = 0;
  long long Ans = 0;
  for (int i = N - 1; i >= 0; i--) {
    if (S.at(i) == '0') zero++;
    if (S.at(i) == '1') {
      int one = 0;
      while (i >= 0 && S.at(i) == '1') {
        one++;
        i--;
      }
      Ans += (long long)one / 2 * zero;
      i++;
    }
  }
  cout << Ans << endl;
}