#include <bits/stdc++.h>
using namespace std;
int read() {
  int x = 0, flag = 1;
  char c = getchar();
  while ((c > '9' || c < '0') && c != '-') c = getchar();
  if (c == '-') flag = 0, c = getchar();
  while (c <= '9' && c >= '0') {
    x = (x << 3) + (x << 1) + c - '0';
    c = getchar();
  }
  return flag ? x : -x;
}
const int maxn = 2005;
int f[maxn][maxn];
char s[maxn][maxn];
int main() {
  int n = read(), m = read();
  for (int i = (1); i <= (int)(n); i++) scanf("%s", s[i] + 1);
  for (int i = (1); i <= (int)(2); i++)
    for (int j = (1); j <= (int)(m); j++) f[i][j] = 1;
  for (int i = (3); i <= (int)(n); i++)
    for (int j = (1); j <= (int)(m); j++) {
      if (j == 1 || j == m) {
        f[i][j] = 1;
        continue;
      }
      if (s[i][j] != s[i - 1][j - 1] || s[i][j] != s[i - 1][j] ||
          s[i][j] != s[i - 1][j + 1] || s[i][j] != s[i - 2][j]) {
        f[i][j] = 1;
        continue;
      }
      int x = 100000;
      x = min(x, f[i - 1][j - 1]);
      x = min(x, f[i - 1][j]);
      x = min(x, f[i - 1][j + 1]);
      x = min(x, f[i - 2][j]);
      f[i][j] = x + 1;
    }
  long long ans = 0;
  for (int i = (1); i <= (int)(n); i++)
    for (int j = (1); j <= (int)(m); j++) ans += f[i][j];
  cout << ans;
  return 0;
}
