#include<bits/stdc++.h>

#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define ll long long
using namespace std;

int main(){
    IOS
    //freopen("output.txt","w",stdout);
    int n,m;
    cin>>n>>m;

    string s[n];

    for(int i=0;i<n;i++){
        cin>>s[i];
    }
    ll HASH[n][m+1];
    memset(HASH,0,sizeof HASH);
    ll p = 31;
    ll mod = 1000000009LL;
    ll p_pow[m+1];
    p_pow[1]=1;
    for(int i=2;i<=m;i++){
        p_pow[i] = (p_pow[i-1] * p)%mod;
    }
    for(int i=0;i<n;i++){

        for(int j=1;j<=m;j++){
            ll temp = ((ll)(s[i][j-1]-'a'+1))*p_pow[j];
            HASH[i][j] = (HASH[i][j-1]+temp)%mod;

        }
    }
    ll ans = 0;
    map<pair<pair<ll,ll> , char> ,ll>mp;
    for(int j=1;j<=m;j++){
        for(int i=0;i<n;i++){
            ll a = HASH[i][j-1]%mod;
            ll b = (HASH[i][m]-HASH[i][j])%mod;
            char cur = s[i][j-1];
            mp[{{a,b },cur}]++;
            for(char ch='a';ch<='z';ch++){
                if(ch!=cur){
                    ans+=mp[{{a, b},ch}];
                }
            }
        }
        mp.clear();

    }
    cout<<ans<<"\n";
}