Problem:
Score : 100 points

Problem Statement

AtCoder Inc. holds a contest every Saturday.

There are two types of contests called ABC and ARC, and just one of them is held at a time.

The company holds these two types of contests alternately: an ARC follows an ABC and vice versa.

Given a string S representing the type of the contest held last week, print the string representing the type of the contest held this week.

Constraints

S is ABC or ARC.

Input

Input is given from Standard Input in the following format:

S

Output

Print the string representing the type of the contest held this week.

Sample Input 1

ABC

Sample Output 1

ARC

They held an ABC last week, so they will hold an ARC this week.

Solution in C (GCC 9.2.1) (judge verdict: Wrong Answer)

int minus[200010],plus[200010];
int a[200010];
int main(){
	int n;
	scanf("%d",&n);
	long long ans=0;
	for(int i=0;i<n;i++)scanf("%d",a+i);
	for(int i=0;i<n;i++){
		if(i+a[i]<=n)ans+=minus[i+a[i]];
		if(i-a[i]>=0)ans+=plus[i-a[i]];
		if(i+a[i]<=n)plus[i+a[i]]++;
		if(i-a[i]>=0)minus[i-a[i]]++;
	}
	printf("%lld",ans);
}