题目描述:
105. Div 3
time limit per test: 0.5 sec.
memory limit per test: 4096 KB
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
水题一枚,谨此对广大娱乐身心的水题们表示感谢。
代码:
#include<iostream>
#include<cstring>
#include<cstdio>
#include<set>
#include<algorithm>
#include<vector>
#include<cstdlib>
#define inf 0xfffffff
#define CLR(a,b) memset((a),(b),sizeof((a)))
using namespace std;
int const nMax = 100010;
typedef long long LL;
typedef pair<LL,LL> pij;
int main()
{
LL n;
cin>>n;
LL m=n/3;
m*=2;
n%=3;
if(n)n--;
m+=n;
cout<<m<<endl;
return 0;
}