#include <bits/stdc++.h>
#include <atcoder/modint>
using namespace std;
using namespace atcoder;
using ll = long long;
using mint =  modint998244353;
#define rep(i,n) for (int i = 0; i < n; i++)
#define rrep(i,n) for (int i = n-1; i >= 0; i--)
#define rep2(i,a,b) for (int i = a; i < b; i++)
#define rrep2(i,a,b) for (int i = a-1; i >= b; i--)
#define rep3(i,a,b,c) for (int i = a; i < b; i+=c)
#define rrep3(i,a,b,c) for (int i = a-1; i >= b; i-=c)
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
template<class T> bool chmax(T &a, T b){if (a < b){a = b;return true;} else return false;}
template<class T> bool chmin(T &a, T b){if (a > b){a = b;return true;} else return false;}
template<class T> T power(T x, ll y){if (y == 0) return 1;T p = pow(x,y/2);if (y%2 == 0) return p*p;else return p*p*x;}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n,m; cin >> n >> m;
    vector<string> S(n), T(2);
    rep(i,n) cin >> S[i];
    rep(i,m){
        if (S[0][i] != S[1][i]){
            T[0] = S[0].substr(0,i+1) + S[1].substr(i,m-i);
            T[1] = S[1].substr(0,i+1) + S[0].substr(i,m-i);
            break;
        }
    }
    int ans = 0;
    rep(i,2){
        string t = T[i];
        bool f = true;
        rep(j,n){
            int id = m;
            rep(k,m){
                if (S[j][k] != t[k]){
                    id = k;
                    break;
                }
            }
            rep2(k,id,m){
                if (S[j][k] != t[k+1]){
                    f = false;
                    break;
                }
            }
        }
        if (f) ans++;
    }
    cout << ans << endl;
}