UVA - 10375 - Choose and divide

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.math.MathContext;
import java.math.RoundingMode;
import java.util.StringTokenizer;

public class Main {

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringBuffer sb = new StringBuffer("");
        String m="";
        while((m=br.readLine())!=null){
            StringTokenizer st=new StringTokenizer(m);
            int p=Integer.parseInt(st.nextToken());
            int q=Integer.parseInt(st.nextToken());
            int r=Integer.parseInt(st.nextToken());
            int s=Integer.parseInt(st.nextToken());
            BigInteger bg=c(p,q).multiply(BigInteger.valueOf(1000*1000));
            BigInteger bg2=c(r,s);
            bg=bg.divide(bg2);
            double ans=bg.doubleValue();
            ans/=1000000;
            String formattedString = String.format("%.5f\n", ans);
            sb.append(formattedString);
        }
        System.out.print(sb);
    }
   
    static BigInteger c(long n, long r) {
        BigInteger ans = BigInteger.ONE;
        r = Math.min(r, n - r);
        long i;
        for (i = 1; i < r+1; i++) {
            ans=ans.multiply(BigInteger.valueOf(n - r + i));
            ans=ans.divide(BigInteger.valueOf(i));
        }
        return ans;
    }
}