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[AtCoder] Grand Contest 024-A

learningman 5月 20, 2018

A - Fairness

Time limit : 2sec / Memory limit : 1024MB

Score : 300 points

Problem Statement

Takahashi, Nakahashi and Hikuhashi have integers A, B and C, respectively. After repeating the following operation K times, find the integer Takahashi will get minus the integer Nakahashi will get:

Each of them simultaneously calculate the sum of the integers that the other two people have, then replace his own integer with the result.
However, if the absolute value of the answer exceeds 1018, print Unfair instead.

Constraints

1≤A,B,C≤109
0≤K≤10^18
All values in input are integers.

Input

Input is given from Standard Input in the following format:

A B C K

Output

Print the integer Takahashi will get minus the integer Nakahashi will get, after repeating the following operation K times. If the absolute value of the answer exceeds 1018, print Unfair instead.

Sample Input 1

1 2 3 1

Sample Output 1

1
After one operation, Takahashi, Nakahashi and Hikuhashi have 5, 4 and 3, respectively. We should print 5−4=1.

Sample Input 2

2 3 2 0

Sample Output 2

-1

Sample Input 3

1000000000 1000000000 1000000000 1000000000000000000

Sample Output 3

0

Code

#include <bits/stdc++.h>#define LL long longusing namespace std;int main() { LL a,b,c; LL abc; LL k; scanf("%lld %lld %lld %lld",&a,&b,&c,&k); if(k%2==1) printf("%lld",b-a); else printf("%lld",a-b); return 0; }

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