import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.InputMismatchException;
import java.util.List;
import java.util.StringTokenizer;
import java.util.stream.Stream;

public class Main {

	public static void main(String[] args) throws IOException {
		InputStream inputStream = System.in;
		OutputStream outputStream = System.out;
		InputReader in = new InputReader(inputStream);
		PrintWriter out = new PrintWriter(outputStream);
		TaskX solver = new TaskX();
		solver.solve(1, in, out);
		out.close();
	}

	static int INF = 1 << 30;
	static long LINF = 1L << 55;
	static int MOD = 1000000007;
	static int[] mh4 = { 0, -1, 1, 0 };
	static int[] mw4 = { -1, 0, 0, 1 };
	static int[] mh8 = { -1, -1, -1, 0, 0, 1, 1, 1 };
	static int[] mw8 = { -1, 0, 1, -1, 1, -1, 0, 1 };

	@SuppressWarnings("unchecked")
	static class TaskX {

		char[] s;
		int[] visited;
		List<Integer>[] g;
		public void solve(int testNumber, InputReader in, PrintWriter out) {

			int n = in.nextInt();
			int m = in.nextInt();
			s = in.nextString().toCharArray();
			visited = new int[2*n];

			// 頂点倍化して(AABB)*の形の閉路が検出できる有向グラフの形にする
			g = new ArrayList[2*n];
			g = Stream.generate(ArrayList::new).limit(2*n).toArray(List[]::new);
			for (int i = 0; i < m; i++) {
				int a = in.nextInt()-1;
				int b = in.nextInt()-1;
				if (s[a] == s[b]) {
					g[a].add(b + n);
					g[b].add(a + n);
				} else {
					g[a + n].add(b);
					g[b + n].add(a);
				}
			}

			for (int i = 0; i < n; i++) {
				if (visited[i] != 1) dfs(i);
			}

			out.println("No");

		}

		void dfs(int i) {
			visited[i] = -1;
			for (int j : g[i]) {
				if (visited[j] == -1) {
					System.out.println("Yes");
					System.exit(0);
				} else if (visited[j] != 1) {
					dfs(j);
				}
			}
			visited[i] = 1;
		}
	}

	static class InputReader {
		BufferedReader in;
		StringTokenizer tok;

		public String nextString() {
			while (!tok.hasMoreTokens()) {
				try {
					tok = new StringTokenizer(in.readLine(), " ");
				} catch (IOException e) {
					throw new InputMismatchException();
				}
			}
			return tok.nextToken();
		}

		public int nextInt() {
			return Integer.parseInt(nextString());
		}

		public long nextLong() {
			return Long.parseLong(nextString());
		}

		public double nextDouble() {
			return Double.parseDouble(nextString());
		}

		public int[] nextIntArray(int n) {
			int[] res = new int[n];
			for (int i = 0; i < n; i++) {
				res[i] = nextInt();
			}
			return res;
		}

		public int[] nextIntArrayDec(int n) {
			int[] res = new int[n];
			for (int i = 0; i < n; i++) {
				res[i] = nextInt() - 1;
			}
			return res;
		}

		public int[] nextIntArray1Index(int n) {
			int[] res = new int[n + 1];
			for (int i = 0; i < n; i++) {
				res[i + 1] = nextInt();
			}
			return res;
		}

		public long[] nextLongArray(int n) {
			long[] res = new long[n];
			for (int i = 0; i < n; i++) {
				res[i] = nextLong();
			}
			return res;
		}

		public long[] nextLongArrayDec(int n) {
			long[] res = new long[n];
			for (int i = 0; i < n; i++) {
				res[i] = nextLong() - 1;
			}
			return res;
		}

		public long[] nextLongArray1Index(int n) {
			long[] res = new long[n + 1];
			for (int i = 0; i < n; i++) {
				res[i + 1] = nextLong();
			}
			return res;
		}

		public double[] nextDoubleArray(int n) {
			double[] res = new double[n];
			for (int i = 0; i < n; i++) {
				res[i] = nextDouble();
			}
			return res;
		}

		public InputReader(InputStream inputStream) {
			in = new BufferedReader(new InputStreamReader(inputStream));
			tok = new StringTokenizer("");
		}
	}

}


Measured memory_bytes: 119656