import java.util.*;
import java.io.*;
import static java.util.Arrays.*;
import static java.lang.Math.*;

public class No0186 {
    
    static final Scanner in = new Scanner(System.in);
    static final PrintWriter out = new PrintWriter(System.out,false);

    static void solve() {
        boolean[][] f = new boolean[3][3000001];
        for (int i=0; i<3; i++) {
            int x = in.nextInt();
            int y = in.nextInt();
            for (int j=x; j<f[0].length; j+=y) {
                f[i][j] = true;
            }
        }

        for (int i=0; i<f[0].length; i++) {
            if (f[0][i] && f[1][i] && f[2][i]) {
                out.println(i);
                return;
            }
        }
        out.println("-1");
    }

    public static void main(String[] args) {
        long start = System.currentTimeMillis();

        solve();
        out.flush();

        long end = System.currentTimeMillis();
        //trace(end-start + "ms");
        in.close();
        out.close();
    }

    static void trace(Object... o) { System.out.println(deepToString(o));}
}