#include <bits/stdc++.h>

using namespace std;

typedef unsigned long long int n_t;

/*template<typename T>
static void PrintMtx(const vector<vector<T>>& m)
{
    cout << "\n*****************************************" << endl;

    for (int i = 0; i < m.size(); ++i) {
        for (int j = 0; j < m[i].size(); ++j) {
            cout << m[i][j] << ' ';
        }
        cout << endl;
    }
}*/

int main()
{
    ios_base::sync_with_stdio(false);

    string line;
    getline(cin, line);
    stringstream ss(line);
    int n, m;
    ss >> n >> m;

    vector<vector<char>> vec(n, vector<char>(m));

    for (int i = 0; i < n; ++i) {
        getline(cin, line);
        for (int j = 0; j < m; ++j) {
            vec[i][j] = line[j];
        }
    }

    vector<vector<int>> dp1(n, vector<int>(m));
    vector<vector<int>> dp2(n, vector<int>(m));
    vector<vector<int>> dp3(n, vector<int>(m));
    vector<vector<int>> dp4(n, vector<int>(m));

    // ----------------------
    auto s_i = n - 2;
    auto s_j = m - 2;
    int c_i, c_j;
    auto s = 0;

    while (s_i >= 0 && s_j >= 0) {
        c_i = s_i;
        c_j = s_j;

        while (c_i <= n - 2 && c_j >= 0) {
            char a = vec[c_i + 1][c_j];
            char b = vec[c_i][c_j + 1];

            if (a == b && b == vec[c_i][c_j]) {
                dp1[c_i][c_j] = min(dp1[c_i + 1][c_j], dp1[c_i][c_j + 1]) + 1;
                s += dp1[c_i][c_j];
            }

            ++c_i;
            --c_j;
        }

        if (s_i > 0)
            --s_i;
        else
            --s_j;
    }

    // ----------------------
    s_i = 1;
    s_j = 1;

    while (s_i < n && s_j < m) {
        c_i = s_i;
        c_j = s_j;

        while (c_i < n && c_j >= 1) {
            char a = vec[c_i - 1][c_j];
            char b = vec[c_i][c_j - 1];

            if (a == b && b == vec[c_i][c_j]) {
                dp2[c_i][c_j] = min(dp2[c_i - 1][c_j], dp2[c_i][c_j - 1]) + 1;
                s += dp2[c_i][c_j];
            }

            ++c_i;
            --c_j;
        }

        if (s_j < m - 1)
            ++s_j;
        else
            ++s_i;
    }

    // ----------------------
    s_i = n - 2;
    s_j = 1;

    while (s_i >= 0 && s_j < m) {
        c_i = s_i;
        c_j = s_j;

        while (c_i < n - 1 && c_j < m) {
            char a = vec[c_i + 1][c_j];
            char b = vec[c_i][c_j - 1];

            if (a == b && b == vec[c_i][c_j]) {
                dp3[c_i][c_j] = min(dp3[c_i + 1][c_j], dp3[c_i][c_j - 1]) + 1;
                s += dp3[c_i][c_j];
            }

            ++c_i;
            ++c_j;
        }

        if (s_i > 0)
            --s_i;
        else
            ++s_j;
    }
    // ----------------------
    s_i = 1;
    s_j = m - 2;

    while (s_i < n && s_j >= 0) {
        c_i = s_i;
        c_j = s_j;

        while (c_i < n && c_j < m - 1) {
            char a = vec[c_i - 1][c_j];
            char b = vec[c_i][c_j + 1];

            if (a == b && b == vec[c_i][c_j]) {
                dp4[c_i][c_j] = min(dp4[c_i - 1][c_j], dp4[c_i][c_j + 1]) + 1;
                s += dp4[c_i][c_j];
            }

            ++c_i;
            ++c_j;
        }

        if (s_j > 0)
            --s_j;
        else
            ++s_i;
    }

    cout << s << endl;

    return 0;
}