#include<bits/stdc++.h>
using namespace std;
#define lowbit(x) x&(-x)
#define int long long

const int N = 2e5+10;
int mod = 1e6+7;
//int mod =  1e9+7;
//int ways[4][2] = {{1,0},{-1,0},{0,1},{0,-1}};

int n,m;

string a[1010],b[1010];

void solve() {
    cin>>n>>m;

    for(int i = 0;i<n;i++) cin>>a[i];
    for(int i = 0;i<n;i++) cin>>b[i];

    int su = 0;

    for(int i = 0;i<n;i++) for(int j = 0;j<m;j++) su += a[i][j] != b[i][j];

    if(su <= (n+m)/2){
        for(int i = 0;i<n;i++) cout<<a[i]<<endl;
        return;
    }

    for(int i = 0;i<n;i++) for(int j = 0;j<m;j++){
        if(a[i][j] == 'X') a[i][j] = '.';
        else a[i][j] = 'X';
    }

    su = 0;

    for(int i = 0;i<n;i++) for(int j = 0;j<m;j++) su += a[i][j] != b[i][j];

    if(su <= (n+m)/2){
        for(int i = 0;i<n;i++) cout<<a[i]<<endl;
        return;
    }

    cout<<-1<<endl;


}
signed main() {
    std::ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cout<<fixed<<setprecision(10);
    int caset = 1;
    //cin>>caset;

    for(int i = 1;i<=caset;i++){
		solve();
	}

    return 0;
}