#include <iostream>
#include <string>
#include <cmath>
#include<algorithm>
#include<stack>
#include<queue>
#include<map>
#include<set>
#include<iomanip>
#define _USE_MATH_DEFINES
#include <math.h>
#include <functional>
using namespace std;

#define rep(i,x) for(ll i=0;i<x;i++)
#define repn(i,x) for(ll i=1;i<=x;i++)

typedef long long ll;
const ll INF = 1e17;
const ll MOD = 1000000007;
const ll MAX = 4000001;

ll max(ll a, ll b) {
	if (a > b) { return a; }
	return b;
}

ll min(ll a, ll b) {
	if (a > b) { return b; }
	return a;
}

ll gcd(ll a, ll b) {
	if (b == 0) { return a; }
	if (a < b) { return gcd(b, a); }
	return gcd(b, a % b);
}

ll lcm(ll a, ll b) {
	return a / gcd(a, b) * b;
}

struct edge {
	ll ind;
	ll fr;
	ll to;
	ll d;
};

class mint {
    long long x;
public:
    mint(long long x = 0) : x((x% MOD + MOD) % MOD) {}
    mint operator-() const {
        return mint(-x);
    }
    mint& operator+=(const mint& a) {
        if ((x += a.x) >= MOD) x -= MOD;
        return *this;
    }
    mint& operator-=(const mint& a) {
        if ((x += MOD - a.x) >= MOD) x -= MOD;
        return *this;
    }
    mint& operator*=(const  mint& a) {
        (x *= a.x) %= MOD;
        return *this;
    }
    mint operator+(const mint& a) const {
        mint res(*this);
        return res += a;
    }
    mint operator-(const mint& a) const {
        mint res(*this);
        return res -= a;
    }
    mint operator*(const mint& a) const {
        mint res(*this);
        return res *= a;
    }

    mint operator^(const ll& t)const {
        if (!t) return 1;
        mint a = pow(t >> 1);
        a *= a;
        if (t & 1) a *= *this;
        return a;
    }

    mint pow(ll t) const {
        if (!t) return 1;
        mint a = pow(t >> 1);
        a *= a;
        if (t & 1) a *= *this;
        return a;
    }
    // for prime MOD
    mint inv() const {
        return pow(MOD - 2);
    }
    mint& operator/=(const mint& a) {
        return (*this) *= a.inv();
    }
    mint operator/(const mint& a) const {
        mint res(*this);
        return res /= a;
    }

    friend ostream& operator<<(ostream& os, const mint& m) {
        os << m.x;
        return os;
    }
};

//////////////////////////

int main() {
    ll N, M;
    cin >> N >> M;
    string S;
    cin >> S;
    vector<ll> A(N + 1);
    repn(i, N) {
        if (S[i - 1] == 'A') { A[i] = 0; }
        else { A[i] = 1; }
    }

    vector<vector<ll>> g(N + 1);
    vector<vector<ll>> col(N + 1, vector<ll>(2,0));

    repn(i,M){
        ll a, b;
        cin >> a >> b;
        g[a].push_back(b);
        col[a][A[b]]++;
        if (a != b) {
            g[b].push_back(a);
            col[b][A[a]]++;
        }
    }

    queue<ll> q;
    ll sz = 0;

    vector<ll> b(N + 1, 1);

    repn(i, N) {
        if (col[i][0] == 0 || col[i][1] == 0) {
            q.push(i);
            sz++;
            b[i] = 0;
         }
    }

    while (!q.empty()) {
        ll v = q.front();
        q.pop();

        ll x = A[v];
        for (ll w : g[v]) {
            if (b[w] == 0) { continue; }
            col[w][x]--;
            if (col[w][x] == 0) {
                b[w] = 0;
                q.push(w);
                sz++;
            }
        }
    }

    if (sz == N) { cout << "No"; }
    else { cout << "Yes"; }
	system("PAUSE");
}

Measured memory_bytes: 26108