#include <bits/stdc++.h>
using namespace std;
const int N = 200010;
int n, m;
char s[2020][2020];
int dp[2020][2020], a[2020][2020][2], dp1[2020][2020];
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 0; i < n; ++i) {
    scanf("%s", s[i]);
    for (int j = 0; j < m; ++j) {
      if (j == 0) {
        a[i][j][0] = 0;
      } else {
        if (s[i][j] == s[i][j - 1]) {
          a[i][j][0] = a[i][j - 1][0] + 1;
        } else {
          a[i][j][0] = 0;
        }
      }
    }
    for (int j = m - 1; j >= 0; --j) {
      if (j == m - 1) {
        a[i][j][1] = 0;
      } else {
        if (s[i][j] == s[i][j + 1]) {
          a[i][j][1] = a[i][j + 1][1] + 1;
        } else {
          a[i][j][1] = 0;
        }
      }
    }
    if (i == 0) {
      for (int j = 0; j < m; ++j) {
        dp[i][j] = 0;
      }
    } else {
      for (int j = 0; j < m; ++j) {
        if (s[i - 1][j] == s[i][j])
          dp[i][j] = min(dp[i - 1][j] + 1, min(a[i][j][0], a[i][j][1]));
        else
          dp[i][j] = 0;
      }
    }
  }
  for (int i = n - 1; i >= 0; --i) {
    for (int j = 0; j < m; ++j) {
      if (j == 0) {
        a[i][j][0] = 0;
      } else {
        if (s[i][j] == s[i][j - 1]) {
          a[i][j][0] = a[i][j - 1][0] + 1;
        } else {
          a[i][j][0] = 0;
        }
      }
    }
    for (int j = m - 1; j >= 0; --j) {
      if (j == m - 1) {
        a[i][j][1] = 0;
      } else {
        if (s[i][j] == s[i][j + 1]) {
          a[i][j][1] = a[i][j + 1][1] + 1;
        } else {
          a[i][j][1] = 0;
        }
      }
    }
    if (i == n - 1) {
      for (int j = 0; j < m; ++j) {
        dp1[i][j] = 0;
      }
    } else {
      for (int j = 0; j < m; ++j) {
        if (s[i][j] == s[i + 1][j])
          dp1[i][j] = min(dp1[i + 1][j] + 1, min(a[i][j][0], a[i][j][1]));
        else
          dp1[i][j] = 0;
      }
    }
  }
  long long ans = 0;
  for (int i = 0; i < n; ++i) {
    for (int j = 0; j < m; ++j) {
      dp[i][j] = min(dp[i][j], dp1[i][j]);
      ans += dp[i][j] + 1;
    }
  }
  cout << ans << endl;
}
