Recursion-First Index Of a Number in an Array

Given an array of length N and an integer x, you need to find and return the first index of integer x present in the array. Return -1 if it is not present in the array.
First index means, the index of first occurrence of x in the input array.
Do this recursively. Indexing in the array starts from 0.
Input Format :
Line 1 : An Integer N i.e. size of array
Line 2 : N integers which are elements of the array, separated by spaces
Line 3 : Integer x
Output Format :
first index or -1
Constraints :
1 <= N <= 10^3
Sample Input :
4
9 8 10 8
8
Sample Output :
1

****************************Code*******************************

public class Solution {

	public static int firstIndex(int input[], int x) {
		return firstIndex(input,x,0);
	}
	private static int firstIndex(int input[],int x,int si)
	{
		if(si==input.length-1)
			return -1;
		if(input[si]==x)
			return si;
		int ans=firstIndex(input, x, si+1);
		return ans;
	}
	
}