#include <bits/stdc++.h>
using namespace std;
const int MAXN = 2004;
const int INF = 0x3f3f3f3f;
char s[MAXN][MAXN];
int u[MAXN][MAXN], d[MAXN][MAXN];
int l[MAXN][MAXN], r[MAXN][MAXN];
int dp[MAXN][MAXN];
int n, m;
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 0; i < n; ++i) scanf("%s", s[i]);
  for (int i = 0; i < n; ++i) {
    l[i][0] = 1;
    r[i][m - 1] = 1;
    dp[i][0] = dp[i][m - 1] = 1;
    for (int j = 1; j < m; ++j) {
      if (s[i][j - 1] == s[i][j])
        l[i][j] = l[i][j - 1] + 1;
      else
        l[i][j] = 1;
    }
    for (int j = m - 2; j >= 0; --j) {
      if (s[i][j + 1] == s[i][j])
        r[i][j] = r[i][j + 1] + 1;
      else
        r[i][j] = 1;
      dp[i][j] = min(l[i][j], r[i][j]);
    }
  }
  for (int j = 0; j < m; ++j) {
    u[0][j] = 1;
    d[n - 1][j] = 1;
    for (int i = 1; i < n; ++i) {
      if (s[i - 1][j] == s[i][j])
        u[i][j] = min(dp[i][j], u[i - 1][j] + 1);
      else
        u[i][j] = 1;
    }
    for (int i = n - 2; i >= 0; --i) {
      if (s[i + 1][j] == s[i][j])
        d[i][j] = min(dp[i][j], d[i + 1][j] + 1);
      else
        d[i][j] = 1;
    }
  }
  int ans = 0;
  for (int i = 0; i < n; ++i) {
    for (int j = 0; j < m; ++j) {
      ans += min(u[i][j], d[i][j]);
    }
  }
  printf("%d\n", ans);
  return 0;
}
