The mutual arrangement of lines#1835
N. sits at point of some straight line and can move at a speed . On the other (or the same) line at point , there is X, which is passionately desired by N.
Help N. determine the minimum time needed to reach X. Note that N. must remain on one of the two lines at all times.
The input file contains 5 lines:
Six numbers x_{11}, y_{11}, z_{11}, x_{12}, y_{12}, z_{12} — the coordinates of two distinct points on the first line.
Six numbers x_{21}, y_{21}, z_{21}, x_{22}, y_{22}, z_{22} — the coordinates of two distinct points on the second line.
Three numbers a_1, b_1, c_1 — the coordinates of N.
Three numbers a_2, b_2, c_2 — the coordinates of X.
— the velocity of N.
All numbers are integers and their absolute values do not exceed 10^6. It is guaranteed that both N. and X are each on one of the lines.
Output the minimum time required for N. to reach X, with five digits after the decimal point. If N. cannot reach X, output "-1".
Example 1