Which is the least amount of time William needs to reach his nest?

h2. Date de intrare

The first line of the input file $police.in$ contains 4 integers: $N$ (the number of semaphores), $R$ (the number of semaphores William can skip), $T$ (the half-period of the semaphores), and $L$ (the length of the street).

The second line contains $N$ integers: the coordinates $X_i$.

The second line contains $N$ integers: the coordinates X[i].
 

h2. Date de ieşire