There is a string S of length N consisting of characters 0 and 1. You will perform the following operation for each i = 1, 2, ..., m:
- Arbitrarily permute the characters within the substring of S starting at the l_i-th character from the left and extending through the r_i-th character.
Here, the sequence l_i is non-decreasing.
How many values are possible for S after the M operations, modulo 1000000007(= 10^9+7)?

-----Constraints-----
- 2≦N≦3000
- 1≦M≦3000
- S consists of characters 0 and 1.
- The length of S equals N.
- 1≦l_i < r_i≦N
- l_i ≦ l_{i+1}

-----Input-----
The input is given from Standard Input in the following format:
N M
S
l_1 r_1
:
l_M r_M

-----Output-----
Print the number of the possible values for S after the M operations, modulo 1000000007.

-----Sample Input-----
5 2
01001
2 4
3 5

-----Sample Output-----
6

After the first operation, S can be one of the following three: 01001, 00101 and 00011.
After the second operation, S can be one of the following six: 01100, 01010, 01001, 00011, 00101 and 00110.

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