#include<bits/stdc++.h>
using namespace std;
long long a[100001];
long long n,x;
bool f=false;
long long ans;
int main(){
    for(int i=1;i<=n;i++){
    	cin>>a[i];
    }
    for(int i=1;i<=n;i++){
    	if(x==a[i]){
    		ans=i;
    		f=true;
    		break;
    	}
    }
    if(f==true){
    	cout<<ans<<endl;
    }else{
    	cout<<"-1"<<endl;
    }
}
/**************************************************************
	Problem: 1236
	User: zengdongxin
	Language: C++
	Result: Wrong Answer
****************************************************************/