#include<bits/stdc++.h> using namespace std; int n,a[20000],x,p; int main(){ cin>>n; for(int i=0;i<n;i++){ cin>>a[i]; } cin>>x; a[n]=x; while(a[p]!=x)p++; if(p==n)cout<<"-1"; else cout<<p; return 0; }