Разрезание квадрата

#define _USE_MATH_DEFINES
#include <iostream>
#include <string>
#include <map>
#include <set>
#include <algorithm>
#include <vector>
#include <stdio.h>
#include <cmath>
#include <math.h>
#include <queue>
#include <stack>
#include <climits>
#include <deque>
#include <ctime>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef unsigned int ui;

#define mh() make_heap()
#define poph() pop_heap()
#define pushh() push_heap()
#define sor(n) n.begin(), n.end()
#define mp make_pair
#define files freopen("input.txt", "rt", stdin); freopen("output.txt", "wt", stdout)
#define p(T) pair<T,T>
#define znac(l) abs(l)/l
const ll ok = ll(1e9 + 7);
short str[1001][1001];
int main()
{
    //files;
    int n;
    cin >> n;

    for (int i = 1; i <= n; i++)
    {
        string s;
        cin >> s;
        for (int j = 1; j <= n; j++)
        {
            str[i][j] = s[j - 1] - '0';
        }
    }

    ll last = -1;
    bool bad = 0;
    bool exit = 0;
    for (int x = 1; x <= n; x++)
    {
        last = str[x][1];
        bad = 0;
        for (int y = 1; y <= n; y++)
        {
            if (str[x][y] != last)
            {
                if (!bad)
                    bad = 1;
                else
                {
                    exit = 1;
                    break;
                }
            }
            last = str[x][y];
        }
        if (exit)
            break;
    }
    if (!exit)
    {
        cout <<"Yes";
        return 0;
    }

    bad = 0;
    exit = 0;
    for (int y = 1; y <= n; y++)
    {
        last = str[1][y];
        bad = 0;
        for (int x = 1; x <= n; x++)
        {
            if (str[x][y] != last)
            {
                if (!bad)
                    bad = 1;
                else
                {
                    exit = 1;
                    break;
                }
            }
            last = str[x][y];
        }
        if (exit)
            break;
    }

    if (!exit)
    {
        cout << "Yes";
    }
    else
        cout << "No";

    return 0;
}