#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b, k, j = 0;
  char c;
  while (cin >> c) {
    cout << c << endl;
    if (c == '0')
      a++;
    else
      b++;
  }
  cout << 2 * min(a, b) << endl;
}
