Score : 400 points
We have N bricks arranged in a row from left to right.
The i-th brick from the left (1 \leq i \leq N) has an integer a_i written on it.
Among them, you can break at most N-1 bricks of your choice.
Let us say there are K bricks remaining. Snuke will be satisfied if, for each integer i (1 \leq i \leq K), the i-th of those brick from the left has the integer i written on it.
Find the minimum number of bricks you need to break to satisfy Snuke's desire. If his desire is unsatisfiable, print -1
instead.
Input is given from Standard Input in the following format:
N a_1 a_2 ... a_N
Print the minimum number of bricks that need to be broken to satisfy Snuke's desire, or print -1
if his desire is unsatisfiable.
3 2 1 2
1
If we break the leftmost brick, the remaining bricks have integers 1 and 2 written on them from left to right, in which case Snuke will be satisfied.
3 2 2 2
-1
In this case, there is no way to break some of the bricks to satisfy Snuke's desire.
10 3 1 4 1 5 9 2 6 5 3
7
1 1
0
There may be no need to break the bricks at all.