Educational DP Contest AtCoder T - Permutation

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Points: 15
Time limit: 1.0s
Memory limit: 1G

Problem type

Let N be a positive integer. You are given a string s of length N-1, consisting of < and >.

Find the number of permutations (p_1, p_2, \dots, p_N) of (1, 2, \dots, N) that satisfy the following condition, modulo 10^9+7:

  • For each i (1 \le i \le N-1), p_i < p_{i+1} if the i-th character in s is < and p_i > p_{i+1} if the i-th character in s is >.

Constraints

  • N is an integer.
  • 2 \le N \le 3000
  • s is a string of length N-1.
  • s consists of < and >.

Input Specification

The first line will contain the integer N.

The second line will contain the string s.

Output Specification

Print the number of permutations that satisfy the condition, modulo 10^9+7.

Note: Be sure to print the number modulo 10^9+7.

Sample Input 1

4
<><

Sample Output 1

5

Explanation For Sample 1

There are five permutations that satisfy the condition, as follows:

  • (1, 3, 2, 4)
  • (1, 4, 2, 3)
  • (2, 3, 1, 4)
  • (2, 4, 1, 3)
  • (3, 4, 1, 2)

Sample Input 2

5
<<<<

Sample Output 2

1

Explanation For Sample 2

There is one permutation that satisfies the condition, as follows:

  • (1, 2, 3, 4, 5)

Sample Input 3

20
>>>><>>><>><>>><<>>

Sample Output 3

217136290

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