#!/usr/bin/env python3
"""Convert a length in metres to feet and inches (whole inches, round-half-up)."""
import sys

IN_PER_M = 1.0 / 0.0254  # 1 in = 0.0254 m exactly


def m_to_ft_in(m: float) -> tuple[int, int]:
    total = int(m * IN_PER_M + 0.5)  # round-half-up on total inches
    return total // 12, total % 12


def main(argv):
    if len(argv) != 2:
        sys.stderr.write("usage: convert.py <metres>\n")
        return 1
    raw = argv[1].rstrip("mM")
    try:
        m = float(raw)
    except ValueError:
        sys.stderr.write(f"error: '{argv[1]}' is not a number\n")
        return 1
    if m < 0:
        sys.stderr.write("error: length must be non-negative\n")
        return 1
    ft, inch = m_to_ft_in(m)
    print(f"{ft} ft {inch} in")
    return 0


if __name__ == "__main__":
    sys.exit(main(sys.argv))