import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

N,M = map(int,readline().split())
words = '$' + readline().decode().rstrip()
m = map(int,read().split())
UV = tuple(zip(m,m))

MOD = 10**9 + 7

UV += tuple((v,u) for u,v in UV)

dp = [1 * (s == 'P') for s in words] 

for T in 'DCA':
    newdp = [0] * (N+1)
    for u,v in UV:
        if words[v] == T:
            newdp[v] += dp[u]
    dp = newdp

answer = sum(dp) % MOD
print(answer)