ac

#include<bits/stdc++.h>
using namespace std;
int a[1010];
int n;
int binary(int a[],int target){
int l=1,r=n;

while(l<=r){
	int mid=(l+r)/2;
	if(a[mid]==target)return mid;
	else if(a[mid]<target)l=mid+1;
	else{r=mid-1;}
}return -1;

}
int main(){
int x;
scanf("%d",&n);
for(int i=1;i<=n;i++){
scanf("%d",&a[i]);
}scanf("%d",&x);
cout<<binary(a,x);

return 0;

}