Codeforces Round #818 (Div. 2)
A

#include <iostream>
#include <cstring>
#include <algorithm>
#include <unordered_map>
using namespace std;

int n;
int main()
{
    int t;
    cin>>t;
    while(t--){
        cin>>n;
        long long res=0;
        res=n+n/2*2+n/3*2;
        cout<<res<<endl;
    }
}

B

#include <iostream>
#include <cstring>
#include <algorithm>
#include <unordered_map>
using namespace std;
const int N = 510;
bool st[N][N];
int n;
int main()
{
    int t;
    cin>>t;
    while(t--){
        memset(st,false,sizeof(st));
        int n,k,x,y;
        cin>>n>>k>>x>>y;
        for(int i=x,j=y;;){
            st[x][y]=true;
            x--;
            y++;
            if(x==0) x=n;
            if(y==n+1) y=1;
            if(st[x][y]){
                y=(y+k-1)%n+1;
                if(st[x][y]) break;
            }
        }
        for(int i=1;i<=n;i++){
            for(int j=1;j<=n;j++)
                if(st[i][j])cout<<"X";
                else cout<<".";
            puts("");
        }
    }
}