Encounter such problems, you can step by step.

1, look at the first side of the square first. Starting from the vertex, insert a flag every 5 meters, so insert 200/5+1=4 1.

2. Look at the second side. Because its starting point coincides with the end point of the first side, this side only needs to be planted with 200/5=40 flags.

The third side is the same as the second side, so the flag should be inserted 200/5=40 sides.

4. The starting point and ending point of the fourth side coincide with the first side and the third side, so this side only needs to plant the flag 200/5- 1=39.

To sum up, * * needs to plant the flag 4 1+40+40+39= 160.