#include <bits/stdc++.h>
using namespace std;
long long zz, zo, oz, oo;
void init() { cin >> zz >> zo >> oz >> oo; }
vector<long long> pt;
void process() {
  if (zz == 0 && zo == 0 && oz == 0 && oo == 0) {
    puts("1");
    return;
  }
  for (long long i = 0; i <= 1000000; i++) {
    pt.push_back(i * (i - 1) / 2);
  }
  if (find(pt.begin(), pt.end(), zz) == pt.end() ||
      find(pt.begin(), pt.end(), oo) == pt.end()) {
    puts("Impossible");
    return;
  }
  long long nz = find(pt.begin(), pt.end(), zz) - pt.begin();
  long long no = find(pt.begin(), pt.end(), oo) - pt.begin();
  if (nz <= 1) {
    nz = (oz + zo != 0) ? 1 : 0;
  }
  if (no <= 1) {
    no = (oz + zo != 0) ? 1 : 0;
  }
  if (zo + oz != no * nz) {
    puts("Impossible");
    return;
  }
  vector<char> ans;
  while (no != 0 || nz != 0) {
    if (oz >= nz)
      ans.push_back('1'), oz -= nz, no--;
    else
      ans.push_back('0'), nz--;
  }
  for (char xx : ans) putchar(xx);
  puts("");
}
int main() {
  init();
  process();
  return 0;
}
