help！

#include <bits/stdc++.h>
using namespace std;
char a[26]={'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
int main()
{
    bool flag=false;
    int n,m;
    cin>>n>>m;
    if(m<=10)
    {
        int n1=n;
        while(n1>0)
        {
            if(flag==false and n1%10==0){
                flag=true;
                continue;
            }
            else{
                cout<<n1%10;
            }
            n1=n1/10;
        }
    }
    else
    {
        int n1=n;
        while(n1>0){
            if(n1%m>=10)
            {
                int g=n1%10-10;
                cout<<a[g];
            }
            else{
                cout<<n1%10;
            }
            n1=n1/10;
        }
        cout<<n1<<endl;
    }
}