please i got "rutime error on test 1" with this code any help?? thanks in advance
package graph.party;
import java.util.ArrayList;
import java.util.Scanner;
public class Party2 {
public Party2() {
Scanner in = new Scanner(System.in);
System.out.println("entrez le nombre des employés\n");
int n = in.nextInt();
ArrayList<Integer> tab=new ArrayList<Integer>(n);
for(int i=0;i<n;i++){
tab.add(in.nextInt());
}
int result=0;
for(int j=0;j<n;j++){
int temp=1;int var=tab.get(j);
while(var != -1){var=tab.get(var-1);temp++;}
if(temp>result) result=temp;
}
System.out.println(result);
}
public static void main(String[] args) {
new Party2();
}
}