#include <bits/stdc++.h>
using namespace std;
void fastIO() {
  std::ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
}
template <typename T, typename U>
inline void mnze(T &x, U y) {
  if (y < x) x = y;
}
template <typename T, typename U>
inline void mxze(T &x, U y) {
  if (x < y) x = y;
}
void _scan(int &x) { scanf("%d", &x); }
void _scan(long long &x) { scanf("%lld", &x); }
void _scan(double &x) { scanf("%lf", &x); }
void _scan(char &x) { scanf(" %c", &x); }
void _scan(char *x) { scanf("%s", x); }
template <typename T>
void _scan(vector<T> &v) {
  for (int i = 0; i < (int)v.size(); i++) _scan(v[i]);
}
void scan() {}
template <typename T, typename... U>
void scan(T &head, U &...tail) {
  _scan(head);
  scan(tail...);
}
template <typename T>
void _dbg(const char *sdbg, T h) {
  cerr << sdbg << "=" << h << "\n";
}
template <typename T, typename... U>
void _dbg(const char *sdbg, T h, U... t) {
  while (*sdbg != ',') cerr << *sdbg++;
  cerr << "=" << h << ",";
  _dbg(sdbg + 1, t...);
}
long long MOD = 1e9 + 7;
inline long long Msum(long long x) { return x; }
template <typename... Rest>
inline long long Msum(long long x, Rest... rest) {
  return (x + Msum(rest...)) % MOD;
}
inline long long Mprod(long long x) { return x; }
template <typename... Rest>
inline long long Mprod(long long x, Rest... rest) {
  return x * Mprod(rest...) % MOD;
}
inline long long Mnorm(long long x) { return (x % MOD + MOD) % MOD; }
inline long long Msq(long long x) { return (x * x) % MOD; }
inline long long Mpot(long long x, long long e) {
  if (!e) return 1;
  return Msq(Mpot(x, e >> 1)) * (e & 1 ? x : 1) % MOD;
}
const int MAXN = 2e3 + 3;
char g[MAXN][MAXN];
int x[MAXN][MAXN];
int R, C;
int main() {
  scan(R, C);
  for (int r = 0; r < R; r++) scan(g[r]);
  for (int r = R - 1; r > -1; r--) {
    for (int c = 0; c < C; c++) {
      x[r][c] = 1;
      char cc = g[r][c];
      if (r + 2 >= R) continue;
      if (g[r + 1][c] != cc) continue;
      if (g[r + 2][c] != cc) continue;
      if (c - 1 < 0) continue;
      if (g[r + 1][c - 1] != cc) continue;
      if (c + 1 >= C) continue;
      if (g[r + 1][c + 1] != cc) continue;
      x[r][c] = min(x[r + 2][c], min(x[r + 1][c - 1], x[r + 1][c + 1])) + 1;
    }
  }
  long long ans = 0;
  for (int r = R - 1; r > -1; r--)
    for (int c = 0; c < C; c++) {
      ans += x[r][c];
    }
  printf("%lld\n", ans);
}
