#include <bits/stdc++.h>
using namespace std;
using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
template <typename T, typename S>
inline ostream& operator<<(ostream& os, const pair<T, S> p) {
  cout << "[" << p.first << ";" << p.second << "]";
  return os;
}
template <typename T>
inline ostream& operator<<(ostream& os, const vector<T>& v) {
  for (auto el : v) cout << el << " ";
  return os;
}
template <typename T>
inline ostream& operator<<(ostream& os, const set<T>& v) {
  for (auto el : v) cout << el << " ";
  return os;
}
template <typename T, typename S>
inline ostream& operator<<(ostream& os, const map<T, S>& v) {
  for (auto el : v) cout << el << " ";
  return os;
}
template <typename T>
inline ostream& operator<<(ostream& os, const multiset<T>& v) {
  for (auto el : v) cout << el << " ";
  return os;
}
namespace ___debug {
struct DebugStream {
 private:
  bool is_first;

 public:
  DebugStream(bool _is_first) : is_first(_is_first) {}
  template <typename T>
  DebugStream operator<<(const T& value) const {
    assert(0);
    if (is_first) cout << "[DBG] ";
    cout << value;
    return DebugStream(false);
  };
  template <typename T>
  DebugStream printArray(T* l, T* r) {
    assert(0);
    if (is_first) cout << "[DBG] ";
    while (l != r) {
      cout << (*l);
      ++l;
      if (l == r) {
        cout << '\n';
      } else {
        cout << ' ';
      }
    }
    return DebugStream(false);
  }
};
DebugStream instance(true);
};  // namespace ___debug
const int INT_INF = (int)(2e9);
const ll LL_INF = (ll)(2e18);
const int NIL = -1;
static mt19937 _g(time(nullptr));
inline ll randint(ll a, ll b) {
  ll w = (_g() << 31LL) ^ _g();
  return a + w % (b - a + 1);
}
inline void fast_io() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
};
template <typename T>
inline T sign(T x) {
  return T(x > 0) - T(x < 0);
}
template <typename T>
inline T fetch() {
  T ret;
  cin >> ret;
  return ret;
}
template <typename T>
inline vector<T> fetch_vec(int sz) {
  vector<T> ret(sz);
  for (auto& elem : ret) cin >> elem;
  return ret;
}
template <typename T>
inline void makeUnique(vector<T>& v) {
  sort(v.begin(), v.end());
  v.erase(unique(v.begin(), v.end()), v.end());
}
const int MAXN = 2077;
string A[MAXN];
char M[MAXN][MAXN];
int Up[MAXN][MAXN], Down[MAXN][MAXN];
int DpRight[MAXN][MAXN], DpLeft[MAXN][MAXN];
int n, m;
ll answ = 0;
void solve() {
  cin >> n >> m;
  for (int i = 0; i < n; ++i) {
    cin >> A[i];
  }
  for (char a = 'a'; a <= 'z'; ++a) {
    for (int i = 0; i < n; ++i) {
      for (int j = 0; j < m; ++j) {
        M[i][j] = (A[i][j] == a);
      }
    }
    for (int i = 0; i < n; ++i) {
      for (int j = 0; j < m; ++j) {
        if (M[i][j]) {
          Up[i][j] = 1;
          if (i) {
            Up[i][j] += Up[i - 1][j];
          }
        } else {
          Up[i][j] = 0;
        }
      }
    }
    for (int i = n - 1; i >= 0; --i) {
      for (int j = 0; j < m; ++j) {
        if (M[i][j]) {
          Down[i][j] = 1;
          if (i < n - 1) {
            Down[i][j] += Down[i + 1][j];
          }
        } else {
          Down[i][j] = 0;
        }
      }
    }
    for (int i = 0; i < n; ++i) {
      for (int j = m - 1; j >= 0; --j) {
        if (j < m - 1) {
          DpRight[i][j] = min({Up[i][j], Down[i][j], DpRight[i][j + 1] + 1});
        } else {
          DpRight[i][j] = min({Up[i][j], Down[i][j], 1});
        }
      }
      for (int j = 0; j < m; ++j) {
        if (j) {
          DpLeft[i][j] = min({Up[i][j], Down[i][j], DpLeft[i][j - 1] + 1});
        } else {
          DpLeft[i][j] = min({Up[i][j], Down[i][j], 1});
        }
      }
      for (int j = 0; j < m; ++j) {
        answ += min<ll>(DpLeft[i][j], DpRight[i][j]);
      }
    }
  }
  cout << answ << '\n';
}
int main() {
  fast_io();
  solve();
  return 0;
}
