#include <bits/stdc++.h>
#define NMax 2001
using namespace std;

ifstream f("map.in");
ofstream g("map.out");

int n, m, nr;
char a[NMax][NMax];

int main()
{
    f >> n >> m;
    for(int i = 1; i <= n; ++i)
        for(int j = 1; j <= m; ++j)
            f >> a[i][j];
    for(int i = 1; i <= m / 2; ++i)
        {
            if(a[1][i] == a[1][m - i + 1]) ++nr;
            else if(i != nr)
            {
                g << m << '\n';
                return 0;
            }
        }

    if(nr == 0) g << m << '\n';
    else g << nr + 1 << '\n';
    return 0;
}