import sequtils,strutils,algorithm,math,sugar,macros,strformat
import sets,tables,intsets,queues,heapqueue,bitops
template get*():string = stdin.readLine().strip()
macro unpack*(arr: auto,cnt: static[int]): auto =
  let t = genSym(); result = quote do:(let `t` = `arr`;())
  for i in 0..<cnt: result[1].add(quote do:`t`[`i`])
template times*(n:int,body) = (for _ in 0..<n: body)
proc toCountSeq[T](x:seq[T]) : seq[tuple[k:T,v:int]] = toSeq(x.toCountTable().pairs)
template `max=`*(x,y) = x = max(x,y)
template `min=`*(x,y) = x = min(x,y)

let (n,m) = get().split().map(parseInt).unpack(2)
let S = toSeq(get().items).mapIt:
  case it:
  of 'P':0
  of 'D':1
  of 'C':2
  else : 3
let UV = newSeqWith(m,get().split().map(parseInt)).mapIt((u:it[0]-1,v:it[1]-1))
var DC = newSeq[(int,int)]()
var CA = newSeq[int]()
var ans = newSeq[int](n)
for uv in UV:
  var (u,v) = uv
  if S[u] > S[v]: (u,v) = (v,u)
  if S[v] - S[u] != 1 : continue
  case S[v]:
  of 1 : ans[v] += 1
  of 2 : DC &= (u,v)
  else : CA &= u
for dc in DC: ans[dc[1]] += ans[dc[0]]
echo CA.mapIt(ans[it]).sum() mod 1000000007