import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.math.BigInteger;

public class No201 {

    public static void main(String[] args) {
        try {
            BufferedReader br = new BufferedReader(new InputStreamReader(
                    System.in));
            String[] a = br.readLine().split(" ");
            String[] b = br.readLine().split(" ");
            BigInteger PA = new BigInteger(a[1]);
            BigInteger PB = new BigInteger(b[1]);
            if (PA.compareTo(PB) == 1) {
                System.out.println(a[0]);
            } else if (PA.compareTo(PB) == -1) {
                System.out.println(b[0]);
            } else {
                System.out.println(-1);
            }

        } catch (Exception e) {
            System.err.println("Error:" + e.getMessage());
        }
    }

}