// https://cses.fi/problemset/task/1653
/*
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*/
#include <bits/stdc++.h>
#include <deque>
#include <queue>
#define input ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define endl '\n'
#define fi first
#define se second
#define eb emplace_back
#define pb push_back
#define ce cout << endl
#define FOR(i, l, r) for (ll i = l; i <= r; i++)
#define FOR2(i, l, r) for (ll i = l; i >= r; i--)
using namespace std;
using ll = long long;
using str = string;
using pll = pair<ll, ll>;
using pii = pair<int, int>;
const ll N = 1e5+1;
const ll LOGN = 19;
const int INF = numeric_limits<int>::max();
const ll MOD = 1e9 + 7;
ll dx[] = {1, -1, 0, 0};
ll dy[] = {0, 0, 1, -1};
void solve() {
int n ,m;
cin >> n >> m;
vector<vector<char>> matrix(n+1,vector<char>(m+1,'.'));
for(int i = 1 ; i <= n ; i ++){
for(int j = 1 ; j <= m ; j ++){
cin >> matrix[i][j];
}
}
function<bool(int,int)> inside = [&](int x , int y){
return (x > 0 && x <= n && y > 0 && y <= m && matrix[x][y] != '.');
};
vector<vector<int>> depth(n+1,vector<int>(m+1,0));
deque<pii> q;
q.pb({1,1});
depth[1][1] = 1;
int ans = 0;
while(!q.empty()){
pii cur_node = q.front();
q.pop_front();
ans = max(ans,depth[cur_node.fi][cur_node.se]);
for(int i = 0 ; i < 4 ; i++){
int x = cur_node.fi + dx[i] ,y = cur_node.se + dy[i];
if(inside(x,y) && depth[x][y] == 0){
if(matrix[x][y] == matrix[cur_node.fi][cur_node.se]){
depth[x][y] = depth[cur_node.fi][cur_node.se];
q.push_front({x,y});
}
else{
depth[x][y] = depth[cur_node.fi][cur_node.se] + 1;
q.pb({x,y});
}
}
}
}
cout << ans <<endl;
}
int main() {
input
const bool cap = true;
if (cap)
solve();
else {
ll t;
cin >> t;
while (t--) solve();
}
}
