#include <bits/stdc++.h> using namespace std; typedef long long ll; typedef pair<ll, ll> pii; typedef vector<ll> vi; typedef vector<vi> matrix; #define rep(i, a, b) for(ll i = a; i < b; i++) #define down(i, b, a) for(ll i = b - 1; i >= a; i--) int main(){ ios_base::sync_with_stdio(false); cin.tie(NULL); ll h, w; cin >> h >> w; vector<vector<char>> grid(h, vector<char>(w)); rep(i, 0, h){ rep(j, 0, w){ cin >> grid[i][j]; } } matrix visit(h, vi(w, 0)); queue<pii> next; next.push({0, 0}); while(!next.empty()){ pii top = next.front(); next.pop(); ll x = top.first, y = top.second; if(visit[x][y]) continue; visit[x][y] = 1; if(x != h - 1){ if(grid[x + 1][y] == grid[x][y]) next.push({x + 1, y}); } if(y != w - 1){ if(grid[x][y + 1] == grid[x][y]) next.push({x, y + 1}); } } ll tot = 1; rep(i, 0, h){ rep(j, 0, w){ if(grid[i][j] == grid[0][0] && !visit[i][j]){ tot++; break; } } if(tot > 1) break; } ll prev = tot; rep(i, 0, h){ rep(j, 0, w){ if(grid[i][j] != '.' && grid[i][j] != grid[0][0]){ tot++; break; } } if(tot != prev) break; } cout << tot << endl; }