#include <bits/stdc++.h>
using namespace std;
long long findN(long long n) {
  long long lo = 0, hi = 1e5;
  while (lo <= hi) {
    long long mid = (lo + hi) >> 1;
    if (mid * (mid + 1) / 2 >= n) {
      if (mid * (mid + 1) / 2 == n) return mid + 1;
      hi = mid - 1;
    } else
      lo = mid + 1;
  }
  return -1;
}
void solve() {
  long long zz, zo, oz, oo;
  cin >> zz >> zo >> oz >> oo;
  if (zz + zo + oz + oo == 0) {
    cout << 0 << "\n";
    return;
  }
  long long a = findN(zz), b = findN(oo);
  if (zo + oz + oo == 0 && a != -1) {
    string ans(a, '0');
    cout << ans << "\n";
    return;
  }
  if (zz + zo + oz == 0 && b != -1) {
    string ans(b, '1');
    cout << ans << "\n";
    return;
  }
  if (a == -1 || b == -1 || a * b != zo + oz) {
    cout << "Impossible\n";
    return;
  }
  int i = 0;
  int n = a + b;
  while (i < n) {
    if (zo >= b) {
      cout << 0;
      zo -= b;
      a--;
      i++;
    } else {
      cout << 1;
      oz -= a;
      b--;
      i++;
    }
  }
  cout << "\n";
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  int tc = 1;
  while (tc--) {
    solve();
  }
  return 0;
}
