MTBIT C++

#include <bits/stdc++.h>
using namespace std;
string s[10000],cheo1="",cheo2="",xuat,doc[10000];
int n=0;
vector<string> b;
char a[1000][1000];
void nhap(){
    string s;
    while(cin>>s){
        n++;
        for(int j=1;j<=s.size();j++){
            a[n][j]=s[j-1];
        }
        b.push_back(s);
    }
}
void giai(){
    string s;
    for(int j=1;j<=n;j++){
        s="";
        for(int i=1;i<=n;i++){
            s=s+a[i][j];
            b.push_back(s);
        }
    }
    s="";
    for(int i=1;i<=n;i++){
        s=s+a[i][i];
    }
    b.push_back(s);
    s="";
    for(int i=1;i<=n;i++){
        s=s+a[i][n+1-i];
    }
    b.push_back(s);
    string ma="";
    for(int i=0;i<b.size();i++){
        if(b[i]>ma) ma=b[i];
    }
    cout<<ma;

}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    freopen("b.inp","r",stdin);
    freopen("b.out","w",stdout);
    nhap();
    giai();
}