#include <bits/stdc++.h>
using namespace std;
template <typename T>
void print(T a) {
  for (auto x : a) cout << x << ' ';
  cout << '\n';
}
void solve() {
  int n, m;
  cin >> n >> m;
  char a[n][m];
  short down[n][m], up[n][m];
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      cin >> a[i][j];
      down[i][j] = 0;
      up[i][j] = 0;
    }
  }
  short l[m], r[m];
  for (int j = 0; j < m; j++) up[0][j] = 1;
  int ans = 0;
  for (int i = 1; i < n; i++) {
    for (int j = 0; j < m; j++) {
      if (j == 0 || (a[i][j - 1] != a[i][j]))
        l[j] = j;
      else
        l[j] = l[j - 1];
    }
    for (int j = m - 1; j >= 0; j--) {
      if (j == m - 1 || (a[i][j + 1] != a[i][j]))
        r[j] = j;
      else
        r[j] = r[j + 1];
    }
    for (int j = 0; j < m; j++) {
      int x = 1;
      if (a[i - 1][j] == a[i][j]) x = up[i - 1][j] + 1;
      x = min(x, j - l[j] + 1);
      x = min(x, r[j] - j + 1);
      up[i][j] = x;
    }
  }
  for (int j = 0; j < m; j++) down[n - 1][j] = 1;
  for (int i = n - 2; i >= 0; i--) {
    for (int j = 0; j < m; j++) {
      if (j == 0 || (a[i][j - 1] != a[i][j]))
        l[j] = j;
      else
        l[j] = l[j - 1];
    }
    for (int j = m - 1; j >= 0; j--) {
      if (j == m - 1 || (a[i][j + 1] != a[i][j]))
        r[j] = j;
      else
        r[j] = r[j + 1];
    }
    for (int j = 0; j < m; j++) {
      int x = 1;
      if (a[i + 1][j] == a[i][j]) x = down[i + 1][j] + 1;
      x = min(x, j - l[j] + 1);
      x = min(x, r[j] - j + 1);
      down[i][j] = x;
    }
  }
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      short res = min(up[i][j], down[i][j]);
      ans += res;
    }
  }
  cout << ans << '\n';
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int t = 1;
  for (int i = 0; i < t; i++) {
    solve();
  }
  return 0;
}
