Problem:
Score : 900 points

Problem Statement

You are given an undirected graph consisting of N vertices and M edges.
The vertices are numbered 1 to N, and the edges are numbered 1 to M.
In addition, each vertex has a label, A or B. The label of Vertex i is s_i.
Edge i bidirectionally connects vertex a_i and b_i.

The phantom thief Nusook likes to choose some vertex as the startpoint and traverse an edge zero or more times.
Today, he will make a string after traveling as above, by placing the labels of the visited vertices in the order visited, beginning from the startpoint.

For example, in a graph where Vertex 1 has the label A and Vertex 2 has the label B, if Nusook travels along the path 1 \rightarrow 2 \rightarrow 1 \rightarrow 2 \rightarrow 2, the resulting string is ABABB.

Determine if Nusook can make all strings consisting of A and B.

Constraints

2 \leq N \leq 2 \times 10^{5}

1 \leq M \leq 2 \times 10^{5}

|s| = N

s_i is A or B.

1 \leq a_i, b_i \leq N

The given graph may NOT be simple or connected.

Input

Input is given from Standard Input in the following format:

N M
s
a_1 b_1
:
a_{M} b_{M}

Output

If Nusook can make all strings consisting of A and B, print Yes; otherwise, print No.

Sample Input 1

2 3
AB
1 1
1 2
2 2

Sample Output 1

Yes

Since Nusook can visit Vertex 1 and Vertex 2 in any way he likes, he can make all strings consisting of A and B.

Sample Input 2

4 3
ABAB
1 2
2 3
3 1

Sample Output 2

No

For example, Nusook cannot make BB.

The given graph may not be connected.

Sample Input 3

13 23
ABAAAABBBBAAB
7 1
10 6
1 11
2 10
2 8
2 11
11 12
8 3
7 12
11 2
13 13
11 9
4 1
9 7
9 6
8 13
8 6
4 10
8 7
4 3
2 1
8 12
6 9

Sample Output 3

Yes

Sample Input 4

13 17
BBABBBAABABBA
7 1
7 9
11 12
3 9
11 9
2 1
11 5
12 11
10 8
1 11
1 8
7 7
9 10
8 8
8 12
6 2
13 11

Sample Output 4

No

Solution in Julia (0.5.0) (judge verdict: Accepted)

parseInt(x)=parse(Int,x)
parseMap(x::Array{SubString{String},1})=map(parseInt,x)

function main()
	n,m = readline() |> split |> parseMap
	s = chomp(readline())
	g = [Int[] for i in 1:n]
	ac = zeros(Int,n)
	bc = zeros(Int,n)
	@inbounds for i in 1:m
		a,b = readline() |> split |> parseMap
		if s[a] == 'A'
			ac[b] += 1
		else
			bc[b] += 1
		end
		if s[b] == 'A'
			ac[a] += 1
		else
			bc[a] += 1
		end
		push!(g[a],b)
		push!(g[b],a)
	end
	stack = Int[]
	for i in 1:n
		if ac[i]==0||bc[i]==0
			push!(stack,i)
		end
	end
	l = Int[]
	vst = zeros(Int,n)
	while !isempty(stack)
		x = pop!(stack)
		if vst[x] == 0
	    	vst[x] = 1
		    push!(l,x)
    		@inbounds for i in 1:length(g[x])
	    		if s[x] == 'A'
		    		ac[g[x][i]] -= 1
			    else
    				bc[g[x][i]] -= 1
    			end
	    		if (ac[g[x][i]] == 0 || bc[g[x][i]] == 0)
		    		push!(stack,g[x][i])
    			end
	    	end
		end
	end
	println(length(l)==n?"No":"Yes")
end
main()