SGU - 105 - Div 3 （简单数学题！）

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<=N<=231 - 1).

Output

Write answer to the output.

Sample Input

4

Sample Output

2

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;
}
时间： 2024-11-06 09:33:36

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