E. Balloons
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

Student Bekzat has $$$n$$$ balloons. Each balloon is either red (denoted by the symbol R) or blue (symbol B). He arranged them in a single row and wants to know:

Is it possible, by performing at most one swap of neighboring balloons, to achieve a configuration where after every red balloon immediately follows a blue one?

Input

A single string $$$s$$$ $$$(2 \le |s| \le 100)$$$, consisting only of the symbols R and B.

Output

Print YES if it is possible to obtain the correct sequence with one swap of neighboring balloons, otherwise print NO.

Example
Input
BR
Output
YES