#include <bits/stdc++.h>
using namespace std;
// nichijou
#define REP(i,a,b) for (int i(a); i < (b); ++i)
#define RP(i,n) REP(i,0,n)
#define PER(i,a,b) for(int i((a)-1); i >= (b); --i)
#define PR(i,n) PER(i,n,0)
#define REP1(i,a,b) REP(i,a,(b)+1)
#define RP1(i,n) REP1(i,1,n)
#define PER1(i,a,b) PER(i,(a)+1,b)
#define PR1(i,n) PER1(i,n,1)
#define DO(n) RP(__i,n)
template<class T,class U>
bool cmax(T & a, const U & b) {return a < b ? a = b, 1 : 0;}
template<class T,class U>
bool cmin(T & a, const U & b) {return b < a ? a = b, 1 : 0;}

// data type
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
#define F first
#define S second

// STL container
typedef vector<int> vi;
typedef vector<ll> vll;
#define SZ(a) ((int)(a).size())
#define ALL(a) begin(a), end(a)
#define CLR(a) (a).clear()
#define BK(a) ((a).back())
#define FT(a) ((a).front())
#define DB(a) (a).pop_back()
#define DF(a) (a).pop_front()
#define PB push_back
#define EB emplace_back

/* I gave you my heart and then you turned around. */
void _BG(const char * s) {cerr<<s<<endl;};
template<class T, class ... TT>
void _BG(const char * s,T a, TT...b)
{
	for (int c = 0; *s && (c || *s != ','); ++s) {
		cerr<<*s;
		for (char x : "([{") c += *s == x;
		for (char x : ")]}") c -= *s == x;
	}
	cerr<<" = "<<a;
	if (sizeof...(b)) {
		cerr<<", ";
        ++s;
    }
    _BG(s,b...);
}
#ifdef PR3PONY
#define BG(...) do { \
	cerr << __PRETTY_FUNCTION__ << ':' << __LINE__ << ": "; \
	_BG(#__VA_ARGS__,__VA_ARGS__); \
} while(0)
#else
#define BG(...)
#endif

/* Reading input is now 20% cooler! */
bool RD() {return 1;}
bool RD(char & a) {return scanf(" %c", &a) == 1;}
bool RD(char * a) {return scanf("%s", a) == 1;}
bool RD(double & a) {return scanf("%lf", &a) == 1;}
bool RD(int & a) {return scanf("%d", &a) == 1;}
bool RD(ll & a) {return scanf("%lld", &a) == 1;}

template<class T, class ... TT>
bool RD(T & a, TT & ... b) {return RD(a) && RD(b...);}

/* Do princesses dream of magic sheep? */
#define DR(T,...) T __VA_ARGS__; RD(__VA_ARGS__)
#define RI(...) DR(int,__VA_ARGS__)

/* For it's time for you to fulfill your output. */
void PT(const char & a) {putchar(a);}
void PT(char const * const & a) {fputs(a, stdout);}
void PT(const double & a) {printf("%.16f", a);}
void PT(const int & a) {printf("%d", a);}
void PT(const ll & a) {printf("%lld", a);}

/* The line will last forever! */
template<char s = ' ', char e = '\n'>
void PL() {if (e) PT(e);}
template<char s = ' ', char e = '\n', class T, class ... TT>
void PL(const T & a, const TT & ... b)
{PT(a); if (sizeof...(b) && s) PT(s); PL<s,e>(b...);}

/* Good Luck && Have Fun ! */
const int N = 212345;
int n,m;
char s[N];
vector<int> g[N];
int ok[N][2];
int main()
{
    RD(n,m,s);
    RP(i,m) {
        int a,b;
        RD(a,b);
        --a,--b;
        g[a].PB(b);
        g[b].PB(a);
        ok[a][s[b]-'A']++;
        ok[b][s[a]-'A']++;
    }
    int ans=n;
    queue<int> q;
    RP(i,n)
        if (!ok[i][0] || !ok[i][1]) {
            q.push(i);
            ok[i][0] = ok[i][1] = -1;
        }
    while (SZ(q)) {
        int a = q.front();
        q.pop();
        --ans;
        for (int b : g[a])
            if (--ok[b][s[a]-'A'] == 0) {
                q.push(b);
                ok[b][0] = ok[b][1] = -1;
            }
    }
    PL(ans ? "Yes" : "No");
}


Measured memory_bytes: 12672