105. Div 3
time limit per test: 0.25 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 有数列1，12,123,1234，...12345678901...求从1到N位的这个数种，有几个这样的数能被3整除 样例理解： 12%3=0 123%3=0 output： 2
长度 数 数%3 长%3
1 1 1 1
2 12 0 2
3 123 0 0
4 1234 1 1
5 12345 0 2
6 123456 0 0
7 1234567 1 1
8 12345678 0 2
9 123456789 0 0
然后就找规律了...对于n，n/3*2能得到初步的被3整除的数的个数，如果n%3==2，再加一个