Restore Communication

There are $N$ people lost in a forest, and each person has a radio. The $i$-th person's radio can transmit $K_i$ frequencies. Let the list of frequencies that the $i$-th person can transmit be $F_i = [f_{(i,1)}, f_{(i,2)}, \ldots, f_{(i, K_i)}]$. The $i$-th person and $j$-th person can communicate with each other if **at least** one of the following holds true: 1) They can both transmit a common