include <bits/stdc++.h>

using namespace std; int u[1000005]; int main(){

int n,k;
cin>>n;
for(int i=0;i<n;i++){
	cin>>u[i];
}
cin>>k;
for(int i=0;i<n;i++){
	if(u[i]==k){
		cout<<i+1<<endl;
		return 0;
	}
}
cout<<-1<<endl;
return 0;

}