#include <bits/stdc++.h>

using namespace std;

#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define maxn 1011

typedef long long ll;

char arr[maxn][maxn];
int dp[maxn][maxn];

int main(){
    int n, m;
    ll ans = 0;
    scanf("%d %d\n", &n, &m);
    for(int i = 0; i < n; i++){
       for(int j = 0; j < m; j++)
            scanf("%c", arr[i] + j); 
       scanf("\n");
    }
    
  //  for(int i = 0; i <n; i++)
   // for(int j = 0; j < m; j++)
    //    printf("%c", arr[i][j]);
        
        
    for(int cur = 33; cur <= 126; cur++){
        for(int i = 0; i < n; i++)
            dp[i][m - 1] = 0;
            
        for(int i = 0; i < m; i++)
            dp[n - 1][i] = 0;
            
        for(int i = n - 2; i >= 0; i--){
            for(int j = m - 2; j >= 0; j--){
                dp[i][j] = 0;
                if(arr[i][j] == cur && arr[i + 1][j] == cur && arr[i][j + 1] == cur)
                    dp[i][j] = min(dp[i + 1][j], dp[i][j + 1]) + 1;
                
                ans += dp[i][j];    
            }
        } 
         
        
        for(int i = 0; i < n; i++)
            dp[i][0] = 0;
            
        for(int i = 0; i < m; i++)
            dp[n - 1][i] = 0;
            
        for(int i = n - 2; i >= 0; i--){
            for(int j = 1; j < m; j++){
                dp[i][j] = 0;
                if(arr[i][j] == cur && arr[i + 1][j] == cur && arr[i][j - 1] == cur)
                    dp[i][j] = min(dp[i + 1][j], dp[i][j - 1]) + 1;
                
                ans += dp[i][j];    
            }
        }   
        
        
            
        for(int i = 0; i < n; i++)
            dp[i][0] = 0;
            
        for(int i = 0; i < m; i++)
            dp[0][i] = 0;
            
        for(int i = 1; i < n; i++){
            for(int j = 1; j < m; j++){
                dp[i][j] = 0;
                if(arr[i][j] == cur && arr[i - 1][j] == cur && arr[i][j - 1] == cur)
                    dp[i][j] = min(dp[i - 1][j], dp[i][j - 1]) + 1;
                
                ans += dp[i][j];    
            }
        }   
        
        for(int i = 0; i < n; i++)
            dp[i][m - 1] = 0;
            
        for(int i = 0; i < m; i++)
            dp[0][i] = 0;
            
        for(int i = 1; i < n; i++){
            for(int j = m - 2; j >= 0; j--){
                dp[i][j] = 0;
                if(arr[i][j] == cur && arr[i - 1][j] == cur && arr[i][j + 1] == cur)
                    dp[i][j] = min(dp[i - 1][j], dp[i][j + 1]) + 1;
                
                ans += dp[i][j];    
            }
        }   
    }    
    printf("%lld\n", ans);
    return 0;
}