#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int *> P;
int main() {
  int a = 0, b = 0, k;
  string s;
  cin >> s;
  for (int i = 0; s[i] != '\0'; i++) {
    cout << s[i];
    if (s[i] == '1') {
      a += 1;
    } else if (s[i] == '0') {
      b += 1;
    }
  }
  if (a > b) {
    k = a + b - (a - b);
  } else {
    k = a + b - (b - a);
  }
  cout << k << endl;
  return (0);
}
