C++ :

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<queue>
#include<iostream>
#include<stack>
#include<algorithm>
#include<vector>
#include<iterator>
#include<map>
#include<set>
#include<cmath>
#include<iostream>
#include<string>
using namespace std;
string tr(int x,int y,string s)
{
    string res="";
    int sum=0;
    for(int i=0;i<s.length();++i)
    {
        if(s[i]=='-')
            continue;
        if(s[i]>='0' && s[i]<='9')
            sum=sum*x+s[i]-'0';
        else
            sum=sum*x+s[i]-'a'+10;
    }
    while(sum)
    {
        char tmp=sum%y;
        sum/=y;
        if(tmp<=9)
            tmp+='0';
        else
            tmp=tmp-10+'a';
        res=tmp+res;
    }
    if(res.length()==0)
        res="0";
    if(s[0]=='-')
        res='-'+res;
    return res;
}
inline int mx(int a,int b)
{
    return a>b?a:b;
}
inline int mi(int a,int b)
{
    return a<b?a:b;
}
inline int abs1(int a)
{
    return a>0?a:-a;
}
stack<char> s1;
int main()
{
    string an;
    int tot;
    int a,b;
    while(1)
    {
        while(!s1.empty())
            s1.pop();
        tot=0;
        string s;
        scanf("%d ",&a);
        cin>>s;
        if(a==0 && s=="0")
            break;
        if(a<0)
        {
            int flag=0,tot=0;
            if(s[0]=='-')
            {
                flag=1;
                tot++;
            }
            b=0;
            int w=tot;
            tot=1;
            for(int i=s.length()-1;i>=w;--i)
            {
                b+=(s[i]-'0')*tot;
                tot*=10;
            }
            if(flag==1)
                b=-b;
            while(b)
            {
                int k=b%a;
                if(k<0)
                {
                    k-=a;
                    b/=a;
                    b++;
                }
                else
                    b/=a;
                if(k<10)
                    s1.push(k+'0');
                else
                    s1.push((k-10)+'a');
            }
            while(!s1.empty())
            {
            int k=s1.top();
             printf("%c",k);
              s1.pop();
             }
              printf("\n");
 
        }
        else
        {
            an=tr(10,a,s);
            cout<<an<<endl;
        }
    }
    return 0;
}