There are 30 islands and 150 bridges.
Bridges connected islands.
There are no two bridges which connect the same islands, and there are no isolated islands.
The 15 islands have RED flags, and other 15 islands have BLUE flags.

Now, repeat the following Step 1-3 until all flags are RED or BLUE.

1. Choose one island at random, and call this island "X".
2. From the island which are linked to X, choose one island and call this island "Y".
3. If the color of X flag and the color of Y flag is different, change Y flag color into X flag color.

The probability that all flags become RED is different from How bridges link islands, Find the max probability.
(I'm not good at English, so If there is grammar mistake, please teach me.)