// editor5
#include<stdio.h>
int binarySearch(int arr[],int n,int target){
    int left = 0,right = n-1;
    
    while(left<=right){
        int mid = left+(right-left)/2;
        
        if(arr[mid]==target)
        return mid;
        
        else if(arr[mid]<target)
        left=mid+1;
        else
        right = mid-1;
    }
    retrn 0;
}
    int main(){
        int n,target;
        scanf("%d", &n);
        int arr[n];
        for(int i=0;i<n;i++)
        scanf("%d", &arr[i]);
        
        scanf("%d", &target);
        int result  = binarySearch(arr,n,target);
        printf("%d",result);
        return 0;
}