SGU105—— Div 3

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

3

 

找规律：

 

易得：  要求的数=n/3*2;

#include<iostream>#include<string.h>#include<stdio.h>#include<ctype.h>#include<algorithm>#include<stack>#include<queue>#include<set>#include<math.h>#include<vector>#include<map>#include<deque>#include<list>using namespace std;int main(){    int n,sum;    while(scanf("%d",&n)!=EOF)    {       sum=(double)n/3*2;       printf("%d\n",sum);    }    return 0;}