what is wrong with code?
package pl.codegym.task.task15.task1531;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigInteger;
/*
Silnia
*/
public class Solution {
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
int input = Integer.parseInt(reader.readLine());
reader.close();
System.out.println(factorial(input));
}
public static String factorial(int n) {
BigInteger result = BigInteger.ONE;
if(n <= 0){
//result = result.intValue(0);
System.out.println("0! = 1");
}
else {
for (int i = 2; i <= n; i++)
result = result.multiply(BigInteger.valueOf(i));
}
return String.valueOf(result);
}
}