whar is wrong
package com.codegym.task.task15.task1531;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigDecimal;
import java.math.BigInteger;
/*
Factorial
*/
public class Solution {
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
int input = BigInteger.parseInt(reader.readLine());
reader.close();
if (input<151)
System.out.println(factorial(input));
}
public static String factorial(int n) {
//write your code here
int r=0;
if (n==0||n==1||n<0) r=1;
if (n>1) r= BigInteger.parseInt(factorial(n-1))*n;
return BigInteger.toString(r);
}
}