#include <iostream>
#include <vector>
using namespace std;

int main()
{
    vector<int> a;
    
    int n,m;
    cin>>n;
    int b;
    for (int i = 0; i < n; ++i)
    {
        cin >> b;
        a.push_back(b);
    }
    cin >> m;
    for (int i = 0; i < n; ++i)
    {
        if (a[i] == m)
        {
            cout << i;
            return 0;
        }
    }
    cout << "No";
    return 0;
}