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Codeforces Round #277 (Div. 2)-A. Calculating Function (规律)_html/css_WEB-ITnose

程序员文章站 2022-05-21 12:10:29
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Calculating Function

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

For a positive integer n let's define a function f:

f(n)?=??-?1?+?2?-?3?+?..?+?(?-?1)nn

Your task is to calculate f(n) for a given integer n.

Input

The single line contains the positive integer n (1?≤?n?≤?1015).

Output

Print f(n) in a single line.

Sample test(s)

input

output

input

output

-3

Note

f(4)?=??-?1?+?2?-?3?+?4?=?2

f(5)?=??-?1?+?2?-?3?+?4?-?5?=??-?3






解题思路:大水题一枚,直接找规律。n%2==0时,f = n/2; 否则,f = -(n+1)/2.





AC代码:

#include #include #include #include #include #include #include #include #include #include #include #include using namespace std;#define INF 0x7fffffffint main(){//    #ifdef sxk//        freopen("in.txt","r",stdin);//    #endif    long long n;    while(scanf("%lld",&n)!=EOF)    {        if(n & 1) printf("%lld\n", -(n+1)/2);        else printf("%lld\n", n/2);    }    return 0;}