<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def roughsize(size, above=20, mod=10):
 """6 -> '6' 15 -> '15' 134 -> '130+'."""

    if size < above:
        return str(size)

    return "{:d}+".format(size - size % mod)