Can anyone give some test cases?

#include<bits/stdc++.h>
using namespace std;
int i, j, k, l, x, y, z, m, n, ans;
string first, second;
int dp[1010][1010][3][4], dir[1010][1010];

int make_way(int first_pile, int second_pile, char c, int state)
{

    //cout << first_pile << ' ' << second_pile << endl;
    if(first_pile == n && second_pile == n){
        if(state > 1) return 0;
        else return 1;
    }


    if(state > 1) return 0;

    int p = 0, q = 0, r = 0;
    char d;
    if(c == '0') d = '1';
    else d = '0';

    if(first_pile < n){
        if(first[first_pile] == c){
            p = make_way(first_pile + 1, second_pile, c, state + 1);
        }
        else{
            p = make_way(first_pile + 1, second_pile, d, 1);
        }
    }

    if(second_pile < n){
        if(second[second_pile] == c){
            q = make_way(first_pile , second_pile + 1, c, state + 1);
        }
        else{
            q = make_way(first_pile , second_pile + 1, d, 1);
        }
    }

    if(p == 1){
        dir[first_pile][second_pile] = 1;
    }
    else if(q == 1) dir[first_pile][second_pile] = 2;

    dp[first_pile][second_pile][c - '0'][state] = p | q;

    return dp[first_pile][second_pile][c - '0'][state];


}

int main()
{
    cin >> n >> first >> second;

    ans = make_way(0, 0, '0', 0);

    if(!ans){
        cout << "Impossible" ;
        return 0;
    }
    for(i = 0, j = 0; i < n || j < n; ){
        cout << dir[i][j];
        if(dir[i][j] == 1) i++;
        else j++;
    }

    return 0;
}