【SGU】105. Div 3 水题

传送门：【SGU】105. Div 3

题目分析：第n个数的数字之和为n*(n + 1)/2。

代码如下：

#include <cstdio>#include <cstring>#include <algorithm>#include <cmath>using namespace std ;#pragma comment(linker, "/STACK:16777216")#define rep( i , a , b ) for ( int i = ( a ) ; i <  ( b ) ; ++ i )#define rev( i , a , b ) for ( int i = ( a ) ; i >= ( b ) ; -- i )#define For( i , a , b ) for ( int i = ( a ) ; i <= ( b ) ; ++ i )#define clr( a , x ) memset ( a , x , sizeof a )#define cpy( a , x ) memcpy ( a , x , sizeof a )int n ;int main () {while ( ~scanf ( "%d" , &n ) ) printf ( "%d\n" , n / 3 * 2 + ( ( n + 1 ) % 3 == 0 ) ) ;return 0 ;}