#include<stdio.h>

int binary_search(int arr[],int n,int target){
    int left = 0,right = - 1;
    
    while (left <= right){
        int mid = left + (right - left)/2;
        
        if(arr[mid] == target){
            return mid;
        }
        if(arr[mid>target]){
            right = mid - 1;
        }
        
        else{
            left = mid = 1;
        }
    }
    return -1;
}

int main(){
    int N;
    scanf("%d",&N);
    
    int arr[N];
    
    for(int i = 0;i< N;i++){
        scanf("%d", &target);
        
        int result = binary_search(arr,N,target);
        printf("&d\n",result);
        
        return 0;
    }
}