Poj Solution 2710

http://poj.org/problem?id=2710

//* @author: ccQ.SuperSupper
import java.util.*;
import java.math.*;
public class Main {
 public static void main(String []args) throws Exception{
        
 int t,cs=1,left,right,i,j;
 BigInteger a,b,seven;
 String str1,str2;
        
 seven = BigInteger.valueOf(1);
 for(i=0;i< 10000;++i)
    seven = seven.multiply(BigInteger.valueOf(7));
        
 Scanner cin = new Scanner(System.in);
        
 t = cin.nextInt();
 while(t--!=0){
    str1 = cin.next();
    str2 = cin.next();
    left = cin.nextInt();
    right = cin.nextInt();
    
    a = new BigInteger(str1);
    a = a.multiply(seven);
    a = a.divide(new BigInteger(str2));
            
    b = new BigInteger(str1);
    b = b.divide(new BigInteger(str2));
    b = b.multiply(seven);
    
    a = a.subtract(b);
    a = a.add(seven);
System.out.print("Problem set "+cs+": "+str1+" / "+str2+", base 7 digits "+left+" through "+right+": ");
    System.out.println(a.toString(7).substring(left+1, right+2));
    ++cs;
  }
 }
}