100pts

#include<bits/stdc++.h>
using namespace std;
const int N = 10005;
int n,m;
int a[N][N];
int main(){
    scanf("%d%d",&n,&m);
    for (register int i = 1;i <= n;++i)
        for (register int j = 1;j <= m;++j)
            scanf("%d",&a[i][j]);
    register int ans = 0;
    for (register int i = 1;i <= n;++i){
        for (register int j = 1;j <= m;++j){
            register int xy = 0;
            while (1){
                xy++;
                bool use = false;
                for (register int sx = i;sx <= xy + i - 1;++sx){
                    for (register int sy = j;sy <= xy + j - 1;++sy){
                        if (sx > n || sy > m){
                            use = true;
                            break;
                        }
                        if (!(a[sx][sy] != a[sx - 1][sy] && a[sx][sy] != a[sx][sy - 1] && a[sx][sy] == a[sx - 1][sy - 1])){
							use = true;
							break;
						}
                    }
                }
                if (!use && xy > ans)ans = xy;
                if (use)break;
            }
        }
    }
    printf("%d",ans + 1); 
    return 0;
}

0pts

#include<bits/stdc++.h>
using namespace std;
const int N = 10005;
int n,m;
int a[N][N];
int main(){
    scanf("%d%d",&n,&m);
    for (register int i = 1;i <= n;++i)
        for (register int j = 1;j <= m;++j)
            scanf("%d",&a[i][j]);
    register int ans = 0;
    for (register int i = 1;i <= n;++i){
        for (register int j = 1;j <= m;++j){
            register int xy = 0;
            while (1){
                xy++;
                bool use = false;
                for (register int sx = i;sx <= xy + i - 1;++sx){
                    for (register int sy = j;sy <= xy + j - 1;++sy){
                        if (sx > n || sy > m){
                            use = true;
                            break;
                        }
                        if (!(a[sx][sy] != a[sx - 1][sy] && a[sx][sy] != a[sx][sy - 1] && a[sx][sy] == a[sx - 1][sy - 1])){
							use = true;
							break;
						}
                    }
                }
                if (!use && xy > ans)ans = xy;
                if (use)break;
            }
        }
    }
    printf("%d",ans); 
    return 0;
}