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 N1, consisting of < and >.

Find the number of permutations (p1,p2,,pN) of (1,2,,N) that satisfy the following condition, modulo 109+7:

  • For each i (1iN1), pi<pi+1 if the i-th character in s is < and pi>pi+1 if the i-th character in s is >.

Constraints

  • N is an integer.
  • 2N3000
  • s is a string of length N1.
  • 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 109+7.

Note: Be sure to print the number modulo 109+7.

Sample Input 1

Copy
4
<><

Sample Output 1

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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

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5
<<<<

Sample Output 2

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1

Explanation For Sample 2

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

  • (1,2,3,4,5)

Sample Input 3

Copy
20
>>>><>>><>><>>><<>>

Sample Output 3

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217136290

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