#include <bits/stdc++.h>
using namespace std;
const int max_n = 2005;
string str[max_n];
int dp[max_n][max_n][4];
inline void solve() {
  register int n, m, i, j, k;
  long long ans = 0;
  cin >> n >> m;
  for (i = 0; i < n; ++i) cin >> str[i];
  for (i = 0; i < n; ++i) {
    dp[i][0][0] = 1;
    for (j = 1; j < m; ++j) {
      if (str[i][j] == str[i][j - 1])
        dp[i][j][0] = dp[i][j - 1][0] + 1;
      else
        dp[i][j][0] = 1;
    }
  }
  for (i = 0; i < n; ++i) {
    dp[i][m - 1][1] = 1;
    for (j = m - 2; j >= 0; --j) {
      if (str[i][j] == str[i][j + 1])
        dp[i][j][1] = dp[i][j + 1][1] + 1;
      else
        dp[i][j][1] = 1;
    }
  }
  for (j = 0; j < m; ++j) dp[0][j][2] = 1;
  for (i = 1; i < n; ++i) {
    for (j = 0; j < m; ++j) {
      if (str[i][j] == str[i - 1][j])
        dp[i][j][2] = min(dp[i][j][0], min(dp[i][j][1], dp[i - 1][j][2] + 1));
      else
        dp[i][j][2] = 1;
    }
  }
  for (j = 0; j < m; ++j) dp[n - 1][j][3] = 1;
  for (i = n - 2; i >= 0; --i) {
    for (j = 0; j < m; ++j) {
      if (str[i][j] == str[i + 1][j])
        dp[i][j][3] = min(dp[i][j][2], dp[i + 1][j][3] + 1);
      else
        dp[i][j][3] = 1;
      ans += dp[i][j][3];
    }
  }
  ans += m;
  cout << ans << endl;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  solve();
  return 0;
}
