打表+二分 时间O(log n)

#include<bits/stdc++.h>
using namespace std;
char ch;
inline int read(){
	int ans=0;
	ch=getchar();
	while(ch<'0'||ch>'9')ch=getchar();
	while(ch>='0'&&ch<='9')
		ans=(ans<<1)+(ans<<3)+(ch^'0'),ch=getchar();
	return ans;
}
int a[]={0,23,128,233,338,443,548,653,758,863,968,1073,1178,1283,1388,1493,1598,1703,1808,1913};
int main(){
	int n=read(),l=0,r=19;
	while(l<r){
		int mid=r-(r-l>>1);
		if(n>=a[mid])l=mid;
		else r=mid-1;
	}
	cout<<l;
	return 0;
}