from fractions import Fraction
found = None
for seconds in range(900, 3601):
    moving_a = min(seconds, 1500) + max(seconds - 2100, 0)
    a_position = Fraction(moving_a * 12, 3600)
    b_position = Fraction((seconds - 900) * 18, 3600)
    if a_position == b_position:
        found = (seconds, a_position)
        break
assert found is not None
t, position = found
result = {"seconds_after_A": t, "seconds_after_B": t - 900, "distance_km": str(position)}
import json
print(json.dumps(result, ensure_ascii=False, sort_keys=True))