#include <bits/stdc++.h>

using namespace std;

typedef unsigned long long int n_t;

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

    int n, m;
    cin >> n >> m;

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

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

    vector<vector<int>> dp(n, vector<int>(m));

    n_t s = 0;

    for (int i = n - 2; i >= 0; --i) {
        for (int j = m - 2; j >= 0; --j) {
            auto bottom = vec[i + 1][j];
            auto right = vec[i][j + 1];

            if (bottom == right && bottom == vec[i][j]) {
                dp[i][j] = min(dp[i + 1][j], dp[i][j + 1]) + 1;
                s += dp[i][j];
            }
        }
    }

    vector<vector<int>> dp2(n, vector<int>(m));

    for (int i = 1; i < n; ++i) {
        for (int j = 1; j < m; ++j) {
            auto top = vec[i - 1][j];
            auto left = vec[i][j - 1];

            if (top == left && top == vec[i][j]) {
                dp2[i][j] = min(dp2[i - 1][j], dp2[i][j - 1]) + 1;
                s += dp2[i][j];
            }
        }
    }

    cout << s << endl;

    return 0;
}