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

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