#include<bits/stdc++.h> using namespace std; int a[10005]; int main(){ int n; cin>>n; for(int i=1;i<=n;i++){ cin>>a[i]; } int m; cin>>m; int l=1,r=n; while(l<=r){ int mid = (l+r)/2; if(a[mid] == m){ cout<<mid<<endl; return 0; }else if(a[mid] < m){ l = mid+1; }else{ r = mid-1; } } cout<<"-1\n"; return 0; }