#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), V;
    rep(i,n) cin >> S[i];
    rep(i,m){
        if (S[0][i] != S[1][i]){
            rep(j,2){
                string t = S[0].substr(0,i);
                t += S[j][i];
                bool f = true;
                rep2(k,i,m-1){
                    if (S[j][k+1] != S[1-j][k]) f = false;
                    t += S[1-j][k];
                }
                if (f){
                    t += S[1-j][m-1];
                    V.push_back(t);
                }
            }
            break;
        }
    }
    int ans = 0;
    for (auto s:V){
        set<string> se;
        rep(i,m+1){
            se.insert(s.substr(0,i)+s.substr(i+1,m-i));
        }
        bool f = true;
        rep(i,n){
            if (!se.count(S[i])){
                f = false;
                break;
            }
        }
        if (f) ans++;
    }
    cout << ans << endl;
}