#include <bits/stdc++.h>
using namespace std;
int a00, a01, a10, a11, n, m;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cin >> a00 >> a01 >> a10 >> a11;
  for (int i = 1; i * (i - 1) <= 2 * max(a00, a11); i++) {
    if (i * (i - 1) == 2 * a00) m = i;
    if (i * (i - 1) == 2 * a11) n = i;
  }
  if (!a01 && !a10 && (!a00 || !a11)) {
    for (int i = 0; i < (a00 ? m : n); i++) cout << (a11 > 0);
    if (!(a00 ? m : n)) cout << "Impossible";
    cout << endl;
    return 0;
  }
  if (!n || !m || n * m != a01 + a10) {
    cout << "Impossible\n";
    return 0;
  }
  for (int i = 0; i < a10 / m; i++) cout << 1;
  for (int i = 0; i < m - a10 % m; i++) cout << 0;
  if (a10 % m) cout << 1;
  for (int i = m - a10 % m; i < m; i++) cout << 0;
  for (int i = a10 / m + (a10 % m > 0); i < n; i++) cout << 1;
  cout << endl;
  return 0;
}
