x 进制 的 z 转换成 y 进制
```java
import java.io.*;
import java.math.BigInteger;
import java.util.*;
public class Main{
public static void main(String args[]) throws Exception {
Scanner cin=new Scanner(System.in);
BigInteger x=cin.nextBigInteger();
BigInteger y=cin.nextBigInteger();
String z=cin.next();
BigInteger bas=new BigInteger("1"),ans=new BigInteger("0");
for(int i=z.length()-1;i>=0;i=i-1){
char c=z.charAt(i);
ans=ans.add(bas.multiply(calu(c)));//System.out.println(calu(c));System.out.println(c);
bas=bas.multiply(x);
}
char a[]=new char [200100];
//System.out.println(ans);
//System.out.println(x);System.out.println(y);
int cnt=0;
BigInteger zo=new BigInteger("0");
for(;;){
cnt=cnt+1;
a[cnt]=change(ans.mod(y));
ans=ans.divide(y);
if(ans.compareTo(zo)==0){
break;
}
}
for(int i=cnt;i>=1;i--){
System.out.print(a[i]);
}
}
private static char change(BigInteger mod) {
// TODO Auto-generated method stub
BigInteger zo=new BigInteger("0"),on=new BigInteger("1");
BigInteger i = new BigInteger("0");
char k='0';
for(;k<='9';i=i.add(on)){
if(i.compareTo(mod)==0) return k;
k++;
}
k='A';
for(;k<='Z';i=i.add(on)){
if(i.compareTo(mod)==0) return k;
k++;
}
k='a';
for(;k<='z';i=i.add(on)){
if(i.compareTo(mod)==0) return k;
k++;
}
return k;
}
private static BigInteger calu(char c) {
// TODO Auto-generated method stub
char m='0'; BigInteger w=new BigInteger("1");
int k=0;
for(BigInteger i=new BigInteger("0");k<=9;i=i.add(w)){
if(m==c) return i;
m++;k++;
}
k=1;m='A';
for(BigInteger i=new BigInteger("10");k<=26;i=i.add(w)){
//System.out.println(i);
if(m==c) {return i;}
m++;k++;
}
k=1;m='a';
for(BigInteger i=new BigInteger("36");k<=26;i=i.add(w)){
if(m==c) return i;
m++;k++;
}
return w;
}
}