17 points are connected in three colors (assuming red, green and blue). If there is a triangle with the same color, the problem is proved.

There are 16 line segments from a certain point, at least 6 of which are of one color. Because, 6+5+5 = 16.

Suppose this point is O, and the connection points of six line segments with the same color (suppose red) are A 1, A2, A3 ..., A6.

If there is a red line connecting A 1 and A2, A3...A5, the red triangle has already appeared.

If there is no red line, there are not less than three lines of a certain color in the connection with A2 and A3 ... A5, because 3+2 = 5, it is assumed that there are not less than three green lines connected with A2 and A3 ... A5 starts from A 1, and its endpoints are assumed to be A 1, A2, A3, and then A65438+.

Complete the certificate.