Consider a circle whose perimeter is divided by N points into N arcs of equal length, and each of the arcs is painted red or blue. Such a circle is said to generate a string S from every point when the following condition is satisfied:

* We will arbitrarily choose one of the N points on the perimeter and place a piece on it.
* Then, we will perform the following move M times: move the piece clockwise or counter-clockwise to an adjacent point.
* Here, whatever point we choose initially, it is always possible to move the piece so that the color of the i-th arc the piece goes along is S_i, by properly deciding the directions of the moves.



Assume that, if S_i is `R`, it represents red; if S_i is `B`, it represents blue. Note that the directions of the moves can be decided separately for each choice of the initial point.

You are given a string S of length M consisting of `R` and `B`. Out of the 2^N ways to paint each of the arcs red or blue in a circle whose perimeter is divided into N arcs of equal length, find the number of ways resulting in a circle that generates S from every point, modulo 10^9+7.

Note that the rotations of the same coloring are also distinguished.

Constraints

* 2 \leq N \leq 2 \times 10^5
* 1 \leq M \leq 2 \times 10^5
* |S|=M
* S_i is `R` or `B`.

Input

Input is given from Standard Input in the following format:


N M
S


Output

Print the number of ways to paint each of the arcs that satisfy the condition, modulo 10^9+7.

Examples

Input

4 7
RBRRBRR


Output

2


Input

3 3
BBB


Output

4


Input

12 10
RRRRBRRRRB


Output

78
n,m = map(int,input().split())
s = input().rstrip()
mod = 10**9+7
if s.count("R") == 0 or s.count("B") == 0:
  dp = [[0 for i in range(2)] for j in range(n)]
  dp[0][0] = 1
  dp[0][1] = 1
  for i in range(1,n):
    dp[i][0] = (dp[i-1][0]+dp[i-1][1])%mod
    dp[i][1] = dp[i-1][0]
  print((dp[n-1][0]+dp[n-2][1])%mod)
  exit()
if n%2:
  print(0)
  exit()
x = s[0]
flg = 1
cnt = 0
ncnt = 0
for i in range(m):
  if s[i] == x:
    cnt += 1
  elif flg == 1:
    flg = 0
    ncnt = cnt
    cnt = 0
  else:
    if cnt%2:
      ncnt = min(ncnt,cnt)
    cnt = 0
if ncnt == 1:
  print(2)
  exit()
y = ncnt//2
dp = [[0 for i in range(2)] for j in range(n//2)]
dp[0][0] = 1
dp[0][1] = 1
for i in range(1,n//2):
  dp[i][0] = dp[i-1][0]+dp[i-1][1]
  if i<y:
    dp[i][1] = dp[i-1][0]+dp[i-1][1]
  elif i == y:
    dp[i][1] = sum([dp[j][0] for j in range(y)])
  else:
    dp[i][1] = dp[i-1][1]+dp[i-1][0]-dp[i-y-1][0]
  dp[i][0] %= mod
  dp[i][1] %= mod
ans = dp[-1][0]+dp[-1][1]
for j in range(1,y+1):
  if n//2-(y+j)-2 >= 0:
    ans = (ans-(dp[n//2-(y+j)-2][0])*(y+1-j))%mod
  elif n//2-(y+j) == 1:
    ans -= y+1-j
print(2*ans%mod)