#include <bits/stdc++.h>
using namespace std;
const int N=1e6+5;
int a[N];
signed main(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	//Thuat toan: Binary search
	//Time complexity :O(log2(N))
	//Author: jixght
	int n;
	cin>>n;
	for(int i=1;i<=n;i++)cin>>a[i];
	int k;
	cin>>k;
	int l=1,r=n;
	while(l<=r){
		int m=(l+r)/2;
		if(a[m]==k){
			cout<<m;
			return 0;
		}
		else if(a[m]<k)l=m+1;
		else r=m-1;
	}
	cout<<0;
}

`color(#FFFFFFff)(H)color(#E7E7E7ff)(o)color(#CFCFCFff)(r)color(#B7B7B7ff)(i)color(#9F9F9Fff)(z)color(#878787ff)(o)color(#6F6F6Fff)(n)`

#include <bits/stdc++.h>
using namespace std;

int main() {
    int n; cin >> n; vector<int> a(n);
    for (auto& i:a) cin >> i;
    int k; cin >> k;
    auto it = find(a.begin(), a.end(), k);
    cout << (it != a.end() ? distance(a.begin(), it) + 1: -1);
}