#include<bits/stdc++.h>
using namespace std;
int main(){
	int m,n,a[105],i,z=0;
	cin>>m;
	for(i=0;i<m;i++){
		cin>>a[i]; 	
	} 
	cin>>n;
	for(i=0;i<m;i++){
		if(a[i]==n)	
		z=1;	
		    cout<<i+1;
			break;		
	}
	if(z==0)
		cout<<"-1";	 

		
	return 0;
}

/**************************************************************
	Problem: 1154
	User: cyp
	Language: C++
	Result: Wrong Answer
****************************************************************/