SGU

SGU - 105

Div 3

Time Limit: 250MS

Memory Limit: 4096KB

64bit IO Format: %I64d & %I64u

Submit Status

Description

There is sequence 1, 12, 123, 1234, ..., 12345678910, ... . Given first N elements of that sequence. You must determine amount of numbers in it that are divisible by 3.

Input

Input contains N (1

Output

Write answer to the output.

Sample Input

Sample Output

Source

数学题！找规律！

规律：0,1,1,0,1,1,0,1,1,0,1,1....      （0代表不能被3整除，1代表能被3整除！）

AC代码：

#include <cstdio>#include <cstring>#include <algorithm>#include <iostream>#include <cmath>using namespace std;int main(){	int n;	scanf("%d", &n);	int ans = 0;	ans += (n/3)*2;	if(n%3==2) ans++;	printf("%d\n", ans);	return 0;} </cmath></iostream></algorithm></cstring></cstdio>