#include
#include
#include
using namespace std;
bool checkValid(int a, int b, int c, int d, vector& zeros, vector& ones) {
int len = zeros.size();
for (int i = 0; i < len; i++) {
if (zeros[i] > a || ones[i] > b || zeros[len + i] > c || ones[len + i] > d) {
return false;
}
}
return true;
}
string generateString(int a, int b, int c, int d, vector& zeros, vector& ones) {
string res;
int len = zeros.size();
for (int i = 0; i < len; i++) {
int cntZero = min(a, zeros[i]);
int cntOne = min(b, ones[i]);
a -= cntZero;
b -= cntOne;
c -= min(c, zeros[len + i]);
d -= min(d, ones[len + i]);
res += string(cntZero, '0') + string(cntOne, '1');
}
res += string(a, '0') + string(b, '1');
return res;
}
string constructString(int a, int b, int c, int d) {
vector zeros(4, 0);
vector ones(4, 0);
for (int i = 0; i < 4; i++) {
zeros[i] = a % 2;
ones[i] = b % 2;
a /= 2;
b /= 2;
}
if (!checkValid(a, b, c, d, zeros, ones)) {
return 'impossible';
}
return generateString(a, b, c, d, zeros, ones);
}
int main() {
int a, b, c, d;
cin >> a >> b >> c >> d;
string res = constructString(a, b, c, d);
cout << res << endl;
return 0;
}
