import java.io.*;

import java.util.*;

public class Main {

static final Reader in = new Reader();

public static void main(String[] args) {

int n=in.nextInt(), m=in.nextInt();

char[] s = in.next().toCharArray();

for(int i=0; i<n; ++i)

s[i]-='A';

List<Integer>[] adj = new List[n];

for(int i=0; i<n; ++i)

adj[i]=new ArrayList<Integer>();

int[][] d = new int[n][2];

for(int i=0; i<m; ++i) {

int u=in.nextInt()-1, v=in.nextInt()-1;

adj[u].add(v);

adj[v].add(u);

++d[u][s[v]];

++d[v][s[u]];

}

boolean[] g = new boolean[n];

int[] qu = new int[n];

int qt=0;

for(int i=0; i<n; ++i) {

if(d[i][0]<=0||d[i][1]<=0) {

g[i]=true;

qu[qt++]=i;

}

}

for(int qh=0; qh<n; ++qh) {

if(qh>=qt) {

System.out.println("Yes");

return;

}

int u=qu[qh];

for(int v : adj[u]) {

if(g[v])

continue;

--d[v][s[u]];

if(d[v][s[u]]<=0) {

g[v]=true;

qu[qt++]=v;

}

}

}

System.out.println("No");

}

static class Reader {

BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

StringTokenizer st;

String next() {

while(st==null||!st.hasMoreTokens()) {

try {

st = new StringTokenizer(br.readLine());

} catch(Exception e) {}

}

return st.nextToken();

}

int nextInt() {

return Integer.parseInt(next());

}

}

}