#include <iostream>
#include <queue>
using namespace std;
char c[4005][4005];
int dx[] = {1, 0, -1, 0}, dy[] = {0, 1, 0, -1}, dd[4005][4005];
int main() {
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n, m, res = 0;
cin >> n >> m;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
cin >> c[i][j];
}
}
queue<pair<int, int>> q;
q.push({1, 1});
dd[1][1] = 1;
while (!q.empty()) {
vector<pair<int, int>> v;
while (!q.empty()) {
pair<int, int> p = q.front();
q.pop();
int x = p.first, y = p.second;
v.push_back({x, y});
for (int i = 0; i < 4; i++) {
int h = x + dx[i], k = y + dy[i];
if (h < 0 || k < 0 || h > n || k > m || c[h][k] != c[x][y] || dd[h][k] == 1) continue;
q.push({h, k});
dd[h][k] = 1;
}
}
for (auto w : v) {
int x = w.first, y = w.second;
for (int i = 0; i < 4; i++) {
int h = x + dx[i], k = y + dy[i];
if (h < 0 || k < 0 || h > n || k > m || c[h][k] == c[x][y] || dd[h][k] == 1) continue;
q.push({h, k});
dd[h][k] = 1;
}
}
res++;
}
cout << res;
}
