四重for,AC了

#include<bits/stdc++.h>
using namespace std;

int main(){
    int n,m;
    cin>>n>>m;
    vector<string>A,B;
    for (int i=0;i<n;i++){
        string s;
        cin>>s;
        A.push_back(s);
    }for (int i=0;i<n;i++){
        string s;
        cin>>s;
        B.push_back(s);
    }
    int count=0;
    for (int x=0;x<=n-m;x++){
        for (int y=0;y<=n-m;y++){
            int diff=0;
            for (int i=0;i<m;i++){
                for (int j=0;j<m;j++){
                    if (A[x + i][y + j] != B[x + i][y + j]){
                        diff++;
                        if (diff>1)break;
                    }
                }
                if (diff>1) break;
            }
            if (diff==1) count++;
        }
    }
    cout<<count;
    return 0;
}