#include<bits/stdc++.h> 
using namespace std;
int main()
{
	int n;
	int a[105];
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>a[i];
	}
	int s;
	cin>>s;
	for(int i=1;i<=n;i++)
	{
		int x=1;
		if(a[i]==s)
		{
			cout<<i;
			x=0
			break;
		}
	}
	if(x==1)
	{
		cout<<"-1";
	}
	return 0;
}
/**************************************************************
	Problem: 1154
	User: wangyuxin
	Language: C++
	Result: Compile Error
****************************************************************/