Score : $300$ points
There are an integer sequence $A_1,...,A_N$ consisting of $N$ terms, and $N$ buttons. When the $i$-th $(1 ≦ i ≦ N)$ button is pressed, the values of the $i$ terms from the first through the $i$-th are all incremented by $1$.
There is also another integer sequence $B_1,...,B_N$. Takahashi will push the buttons some number of times so that for every $i$, $A_i$ will be a multiple of $B_i$.
Find the minimum number of times Takahashi will press the buttons.
The input is given from Standard Input in the following format:
$N$ $A_1$ $B_1$ : $A_N$ $B_N$
Print an integer representing the minimum number of times Takahashi will press the buttons.
3 3 5 2 7 9 4
Press the first button twice, the second button twice and the third button three times.
7 3 1 4 1 5 9 2 6 5 3 5 8 9 7