#include <cstdio>
#include <cstring>
#include <iostream>
using namespace std;

int n,m;
char spotty_cow[105][105];
char plain_cow[105][105];
int ans =0;

int _map[300];
bool s1[5];
bool s2[5];



void init(){
    scanf("%d",&n);
    scanf("%d",&m);
    _map['A'] = 1;
    _map['T'] = 2;
    _map['C'] = 3;
    _map['G'] = 4;
    int i;
    for (i=1;i<=n;i++){
        cin >> spotty_cow[i]+1;
    }
    for (i=1;i<=n;i++){
        cin >> plain_cow[i]+1;
    }
}

bool check(){
    int j;
    for(j = 1;j<=4;j++){
        if( s1[j] == true && s2[j] == true)
            return false;
    }
    return true;
}

int main(){
    init();
    int i,j;
    for (i=1;i<=m;i++){
        memset(s1,0,sizeof(s1));
        memset(s2,0,sizeof(s2));

        for (j=1;j<=n;j++){
            s1[ _map[spotty_cow[j][i]] ] = true;
            s2[ _map[plain_cow[j][i]] ] = true;
        }
        if( check())
            ans++;
    }
    printf("%d",ans);
    return 0;
}