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

int main()
{
    int a,b;
    string s;
    cin>>a>>b;
    while(a>0)
    {
        int o=a%b;
        if(o>=10){
            s+='A'-10+o;
        }else{
            s+='0'+o;
        }
        a/=b;
    }
    reverse(s.begin(),s.end());
    cout<<s;
    return 0; 
}

$CCF4302$

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int N,R;
    cin>>N>>R;
    string ans;
    while(N>0){
        int n=N%R;
        char c;
        if(n < 10) c=n +'0';
        else c=n-10+'A';
        ans+=c;
        N/=R;
    }
    reverse(ans.begin(), ans.end());
    cout << ans;
    return 0;
}