#include<bits/stdc++.h>
using namespace std;
long long n,a[1000005],x;
int main(){
    cin>>n;
    for(int i=1;i<=n;i++){
    	cin>>a[i];
    }
    cin>>x;
    for(int i=1;i<=n;i++){
    	if(a[i]==x){
    		cout<<i;
    		return 0;
    	}
    }
    cout<<-1;
	return 0;
}

/**************************************************************
	Problem: 1236
	User: chenjingqi
	Language: C++
	Result: Accepted
	Time:312 ms
	Memory:9884 kb
****************************************************************/