#include<bits/stdc++.h>
using namespace std;
long s[1000009];
long long a,n;
bool b=false;
int main(){
cin>>a;
for(int i=1;i<=a;i++){
	cin>>s[i];
}
cin>>n;
for(int i=1;i<=a;i++){
	if(s[i]==n){
		cout<<i;
		b=true;
		break; 
	}
}
if(b==false) cout<<-1;
    return 0;
}

/**************************************************************
	Problem: 1236
	User: chenyubo
	Language: C++
	Result: Accepted
	Time:330 ms
	Memory:9884 kb
****************************************************************/