PAT 乙级 1006

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# author: a2htray
# create date: 2023/3/3

"""
PAT 乙级 1006
"""

if __name__ == '__main__':
    chars = [*input()]
    chars.reverse()

    tail = []
    for i in range(1, int(chars[0]) + 1):
        tail.append(str(i))

    bs_list = [[], []]
    for i, char in enumerate(chars[1:]):
        if i == 0:
            bs_list[0] = ['S'] * int(char)
        else:
            bs_list[1] = ['B'] * int(char)

    print(''.join(bs_list[1] + bs_list[0] + tail))