#include <bits/stdc++.h>
using namespace std;
int main(){
	int i,xm=-1;
	cin>>i;
	int o,q[i];
	for(int oo=0;oo<i;oo++)cin>>q[oo];
	cin>>o;
	for(int i2=0;i2<i;i2++){
		if(q[i2]==o){
			cout<<i2+1;
			break;
		}
		if(i2==i-1){
			cout<<-1;
			break;
		}
	}
	return 0;
}

/**************************************************************
	Problem: 1236
	User: zhouhongyi
	Language: C++
	Result: Accepted
	Time:312 ms
	Memory:3896 kb
****************************************************************/