#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define ins insert
#define lb lower_bound
#define F first
#define S second
#define sz size()
#define int long long
#define in insert
#define len(x) (int)x.size()
#define all(v) v.begin(),v.end()
#define FOR(x, n, m, d) for(int x = n; x <= m; x += d)
#define FORR(x, n, m, d) for(int x = n; x >= m; x -= d)
#define nikita ios_base::sync_with_stdio(0), cin.tie(0);
const int N = 1e6 + 15;
int a[N], b[N], n, m, x, y, l, r, k, inf = 1e18, ans, sum, c[N];
void solve(){
cin >> n >> m;
set<char>st;
string s;
FOR(i, 1, n, 1){
cin >> s;
FOR(j, 0, m-1, 1){
if(s[j] == '.')continue;
st.in(s[j]);
}
}
cout << st.sz;
}
signed main(){
nikita
int tt = 1;
// if(tt)cin >> tt;
FOR(i, 1, tt, 1)solve();
}
