Problem:
Score : 700 points

Problem Statement

There are N stones arranged in a row. The i-th stone from the left is painted in the color C_i.

Snuke will perform the following operation zero or more times:

Choose two stones painted in the same color. Repaint all the stones between them, with the color of the chosen stones.

Find the number of possible final sequences of colors of the stones, modulo 10^9+7.

Constraints

1 \leq N \leq 2\times 10^5

1 \leq C_i \leq 2\times 10^5(1\leq i\leq N)

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
C_1
:
C_N

Output

Print the number of possible final sequences of colors of the stones, modulo 10^9+7.

Sample Input 1

5
1
2
1
2
2

Sample Output 1

3

We can make three sequences of colors of stones, as follows:

(1,2,1,2,2), by doing nothing.

(1,1,1,2,2), by choosing the first and third stones to perform the operation.

(1,2,2,2,2), by choosing the second and fourth stones to perform the operation.

Sample Input 2

6
4
2
5
4
2
4

Sample Output 2

5

Sample Input 3

7
1
3
1
2
3
3
2

Sample Output 3

5

Solution in Ruby (2.3.3) (judge verdict: Wrong Answer)

# util functions

# debug
$debugFlag = ( ARGV[0] != nil )
p "==== DEBUG MODE ====" if $debugFlag

# input
lpre = nil
l = $stdin.gets

input = []
while l = $stdin.gets do
  lcur = l.to_i
  next if lpre == lcur
  input << lcur
  lpre = lcur
end

hh = {}
dp = []
input.size.times do |i|
  if i == 0
    dp[i] = 1
    hh[input[i]] = 1
    next
  end
  if hh[input[i]] == nil
    dp[i] = dp[i-1]
    hh[input[i]] = dp[i]
  else
    dp[i] = dp[i-1] + hh[input[i]]
    hh[input[i]] = dp[i]
  end
end

puts dp[-1]