A8020.第一个大于等于x的数

#include<bits/stdc++.h>
using namespace std;
int n,a[110],ans=-1,k,l,r;
int main(){ 
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>a[i];
    }
	cin>>k;
    l=1;
    r=n;
    while(l<=r){
		int mid=l+(r-l)/2;
	    if(k<=a[mid]){
			r=mid-1;
			ans=mid;
		}else{
			l=mid+1;
		}
	}  
	  
	cout<<ans;
    return 0;
}