hdu-1250-Hat's Fibonacci

Hat's Fibonacci

import java.util.Scanner;
import java.math.*;
public class Main {
public static void main(String[] args){
Scanner in=new Scanner(System.in);
BigInteger a,b,c,d,e;

while(in.hasNext()){
a=b=c=d=BigInteger.ONE;
e=BigInteger.ZERO;
int n=in.nextInt();
if(n<=4) System.out.println("1");
else {
for(int i=0;i<n-4;i++){
e=BigInteger.ZERO;
e=e.add(a);
e=e.add(b);
e=e.add(c);
e=e.add(d);
a=b;b=c;c=d;d=e;
}
System.out.println(e);
}
}
in.close();
}
}