题解

#include<iostream>
#include<cmath>
using namespace std;
void base_extern(long long n,int base){
    if(n==0)cout<<"";
    else{
        base_extern(n/base,base);
        if(n%base>=10)cout<<(char)(65+n%base-10);
        else cout<<n%base;
    }
}
int main(){
    int base,ans=0,nbs;
    string s;
    cin>>base>>s>>nbs;
    for(int i=0;i<s.size();i++){
        if(s[i]>='A'&&s[i]<='Z')ans+=(s[i]-55)*pow(base,s.size()-i-1);
        else ans+=(s[i]-48)*pow(base,s.size()-i-1);
    }
    base_extern(ans,nbs);
    return 0;
}