#include <fstream>

#define NMAX 505
using namespace std;

ifstream fin ( "or.in" );
ofstream fout ( "or.out" );

int mat[NMAX][NMAX], L[NMAX], rmq[9][9][NMAX][NMAX];

int query(int stX, int stY, int fsX, int fsY){
    int powX = L[fsX - stX + 1];
    int powY = L[fsY - stY + 1];
    return (rmq[powX][powY][stX][stY] |
            rmq[powX][powY][stX][fsY - (1 << powY) + 1] |
            rmq[powX][powY][fsX - (1 << powX) + 1][stY] |
            rmq[powX][powY][fsX - (1 << powX) + 1][fsY - (1 << powY) + 1]);
}

int main() {
    int x, n;
    fin >> x >> n;

    for ( int i = 1; i <= n; ++i )
        for ( int j = 1; j <= n; ++j ){
            fin >> mat[i][j];
            rmq[0][0][i][j] = mat[i][j];
        }

    for ( int i = 2; i <= n; ++i )
        L[i] = L[i / 2] + 1;

    for(int p = 1; p <= L[n]; ++p)
        for(int i = 1; i <= n; ++i)
            for(int j = 1; j <= n; ++j)
                rmq[p][0][i][j] = (rmq[p - 1][0][i][j] | rmq[p - 1][0][i + (1 << (p - 1))][j]);

    for ( int p = 0; p <= L[n]; ++p )
        for ( int q = 1; q <= L[n]; ++q )
            for ( int i = 1; i <= n; ++i )
                for ( int j = 1; j <= n; ++j )
                    rmq[p][q][i][j] = (rmq[p][q - 1][i][j] | rmq[p][q - 1][i][j + ( 1 << ( q - 1 ) )]);

    fout << query(3, 2, 4, 4);
    return 0;
}