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
#include
#include
using namespace std;
int main()
{
int n,sum;
while(scanf("%d",&n)!=EOF)
{
sum=n/3*2;
if(n%3==2)sum++;
printf("%d\n",sum);
}
return 0;
}