/*
_____
.'     '.
/  0   0  \
|     ^     |
|  \     /  |
\  '---'  /
'._____.'
*/
#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>

using namespace std;
using namespace __gnu_pbds;

struct chash
{
	int operator()(int x) const
	{
		x ^= (x >> 20) ^ (x >> 12);
		return x ^ (x >> 7) ^ (x >> 4);
	}
};

template<typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T, typename U> using hashtable = gp_hash_table<T, U, chash>;
random_device(rd);
mt19937 rng(rd());

template<class T>
void readi(T &x)
{
	T input = 0;
	bool negative = false;
	char c = ' ';
	while (c < '-')
	{
		c = getchar();
	}
	if (c == '-')
	{
		negative = true;
		c = getchar();
	}
	while (c >= '0')
	{
		input = input * 10 + (c - '0');
		c = getchar();
	}
	if (negative)
	{
		input = -input;
	}
	x = input;
}
template<class T>
void printi(T output)
{
	if (output == 0)
	{
		putchar('0');
		return;
	}
	if (output < 0)
	{
		putchar('-');
		output = -output;
	}
	int aout[20];
	int ilen = 0;
	while(output)
	{
		aout[ilen] = ((output % 10));
		output /= 10;
		ilen++;
	}
	for (int i = ilen - 1; i >= 0; i--)
	{
		putchar(aout[i] + '0');
	}
	return;
}
template<class T>
void ckmin(T &a, T b)
{
	a = min(a, b);
}
template<class T>
void ckmax(T &a, T b)
{
	a = max(a, b);
}
template<class T, class U>
T nmod(T &x, U mod)
{
	if (x >= mod) x -= mod;
}
template<class T>
T randomize(T mod)
{
	return (uniform_int_distribution<T>(0, mod - 1))(rng);
}

#define y0 ___y0
#define y1 ___y1
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define PF push_front
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
#define debug(x) cerr << #x << " = " << x << endl;

const long double PI = 4.0 * atan(1.0);
const long double EPS = 1e-10;

#define MAGIC 347
#define SINF 10007
#define CO 1000007
#define INF 1000000007
#define BIG 1000000931
#define LARGE 1696969696967ll
#define GIANT 2564008813937411ll
#define LLINF 2696969696969696969ll
#define MAXN 200013

typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<ld, ld> pdd;

int N, M;
bitset<MAXN> arr, killed;
set<int> edge[MAXN];
bitset<MAXN> ok[2];
int zero[MAXN], one[MAXN];
vector<int> process;

int32_t main()
{
	ios_base::sync_with_stdio(0);
	// cout << fixed << setprecision(10);
	// cerr << fixed << setprecision(10);
	// freopen ("file.in", "r", stdin);
	// freopen ("file.out", "w", stdout);
	cin >> N >> M;
	string temps;
	cin >> temps;
	for (int i = 0; i < N; i++)
	{
		arr[i] = (temps[i] == 'B');
	}
	for (int i = 0; i < M; i++)
	{
		int u, v;
		cin >> u >> v;
		u--; v--;
		edge[u].insert(v);
		edge[v].insert(u);
	}
	// for (int i = 0; i <= 5; i++)
	// {
	// 	ll x = randomize(LLINF);
	// 	ok[0].set();
	// 	ok[1].reset();
	// 	for (int j = 0; j < 60; j++)
	// 	{
	// 		bool bt = (x & (1ll << j));
	// 		for (int k = 0; k < N; k++)
	// 		{
	// 			if (!ok[0][k])
	// 			{
	// 				continue;
	// 			}
	// 			for (int v : edge[k])
	// 			{
	// 				if (arr[v] == bt)
	// 				{
	// 					ok[1][v] = 1;
	// 				}
	// 			}
	// 		}
	// 		swap(ok[0], ok[1]);
	// 		ok[1].reset();
	// 	}
	// 	if (ok[0].count() == 0)
	// 	{
	// 		cout << "No\n";
	// 		return 0;
	// 	}
	// }
	for (int i = 0; i < N; i++)
	{
		for (int v : edge[i])
		{
			if (arr[v] == 0) zero[i]++;
			else one[i]++;
		}
		if (!zero[i] || !one[i])
		{
			process.PB(i);
		}
	}
	while(!process.empty())
	{
		int u = process.back();
		process.pop_back();
		if (killed[u])
		{
			continue;
		}
		killed[u] = true;
		// cerr << "kill " << u << endl;
		for (int v : edge[u])
		{
			if (arr[u] == 0)
			{
				zero[v]--;
				if (zero[v] == 0)
				{
					process.PB(v);
				}
			}
			else
			{
				one[v]--;
				if (one[v] == 0)
				{
					process.PB(v);
				}
			}
			edge[v].erase(u);
		}
	}
	//is there an A that can always go to an either which can always go to an either
	for (int i = 0; i < N; i++)
	{
		if (!killed[i])
		{
			cout << "Yes\n";
			return 0;
		}
	}
	cout << "No\n";
	// cerr << "time elapsed = " << (clock() / (CLOCKS_PER_SEC / 1000)) << " ms" << endl;
	return 0;
}


Measured memory_bytes: 29768