题目描述
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.
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.
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.
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
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分
样例输入
5
1
2
1
2
2
样例输出
3