#include <bits/stdc++.h>
using namespace std;
long long a, b, c, d, o, oo, i, ii, sh;
int main() {
  cin >> a >> b >> c >> d;
  while (sh < a) {
    sh += o;
    o++;
  }
  if (sh != a) {
    cout << "Impossible";
    return 0;
  }
  sh = 0;
  while (sh < d) {
    sh += i;
    i++;
  }
  if (sh != d) {
    cout << "Impossible";
    return 0;
  }
  if (i == 0 && (b != 0 || c != 0)) i = 1;
  if (o == 0 && (i == 0 || (b != 0 || c != 0))) o = 1;
  if (b + c != i * o) {
    cout << "Impossible";
    return 0;
  }
  while (i + o > 0) {
    if (b >= i) {
      cout << 0;
      b -= i;
      o--;
    } else {
      cout << 1;
      i--;
    }
  }
}
