/*
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 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
//package matrice;

import java.util.*;
import java.util.Scanner;


/**
 *
 * @author cteam030
 */
public class Matrice {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        String[] split = sc.nextLine().split(" ");
        int h = Integer.parseInt(split[0]);
        int w = Integer.parseInt(split[1]);
        
        char[][] arr = new char[h][];
        
        for (int i = 0; i < h; i++) {
            arr[i] = sc.nextLine().toCharArray();
        }
        
        int left[][] = new int[h][w];
        int right[][] = new int[h][w];
        
        int left2[][] = new int[h][w];
        int right2[][] = new int[h][w];
        
        
        for (int i = 0; i < h; i++) {
            for (int j = 0; j < w; j++) {

                left[i][j] = 1;
                right[i][j] = 1;
                left2[i][j] = 1;
                right2[i][j] = 1;

            }
        }
        int count = 0;
        for (int i = 1; i < h; i++) {
            for (int j = 0; j < w; j++) {
                // Look left
                if (j > 0) {
                    if (arr[i][j] == arr[i - 1][j - 1] && arr[i][j] == arr[i - 1][j]) {
                       int min = Math.min(left[i - 1][j - 1], left[i - 1][j]);
                       count += min;
                       min++;
                       left[i][j] = min;
                    }
                }
                
                // Look right
                if (j < w - 1) {
                    if (arr[i][j] == arr[i - 1][j] && arr[i][j] == arr[i - 1][j + 1]) {
                       int min = Math.min(right[i - 1][j], right[i - 1][j + 1]);
                       count += min;
                       min++;
                       right[i][j] = min;
                    }
                }
                
                
                
            }
        }
        for (int i = h - 2; i >= 0; i--) {
            for (int j = 0; j < w; j++) {
                // Look bottom left
                if (j > 0) {
                    if (arr[i][j] == arr[i + 1][j - 1] && arr[i][j] == arr[i + 1][j]) {
                        int min = Math.min(left2[i + 1][j - 1], left2[i + 1][j]);
                        count += min;
                        min++;
                        left2[i][j] = min;
                    }
                }

                // Look bottom right
                if (j < w - 1) {
                    if (arr[i][j] == arr[i + 1][j + 1] && arr[i][j] == arr[i + 1][j]) {
                        int min = Math.min(right2[i + 1][j + 1], right2[i + 1][j]);
                        count += min;
                        min++;
                        right2[i][j] = min;
                    }
                }
            }
        }
                
//        for (int i = 0; i < h; i++) {
//            for (int j = 0; j < w; j++) {
//                System.out.print(right[i][j] + "  ");
//            }
//            System.out.println();
//        }
//        
//        for (int i = 0; i < h; i++) {
//            for (int j = 0; j < w; j++) {
//                System.out.print(left[i][j] + "  ");
//            }
//            System.out.println();
//        }
        
        
        System.out.println(count);
        
    }
    
}