#include <bits/stdc++.h>
                                            #include<iostream>
                                            #include<cstdio>
                                            #include<vector>
                                            #include<queue>
                                            #include<map>
                                            #include<cstring>
                                            #include<string>
                                            #include <math.h>
                                            #include<algorithm>
                                        //    #include <boost/multiprecision/cpp_int.hpp>
                                            #include<functional>
                                   #define int long long
                                            #define inf  1000000007
                                            #define pa pair<int,int>
                                            #define ll long long
                                            #define pal pair<double,double>
                                            #define ppap pair<pa,int>
                                    //  #define PI 3.14159265358979323846
                                            #define paa pair<int,char>
                                            #define  mp make_pair
                                            #define  pb push_back
                                            #define EPS (1e-10)
                                            #define equals(a,b) (fabs((a)-(b))<EPS)
    int dx[8]={0,-1,0,1,1,1,-1,-1};
    int dy[8]={1,0,-1,0,-1,1,1,-1};
                                            using namespace std;
                                   			class pa3{
                                            	public:
                                            	int x,y,z;
                                            	pa3(int x=0,int y=0,int z=0):x(x),y(y),z(z) {}
                                            	bool operator < (const pa3 &p) const{
                                            		if(x!=p.x) return x<p.x;
                                            		if(y!=p.y) return y<p.y;
                                            		 return z<p.z;
                                            		//return x != p.x ? x<p.x: y<p.y;
                                            	}
                                   				bool operator > (const pa3 &p) const{
                                            		if(x!=p.x) return x>p.x;
                                            		if(y!=p.y) return y>p.y;
                                            		 return z>p.z;
                                            		//return x != p.x ? x<p.x: y<p.y;
                                            	}
                                            	bool operator == (const pa3 &p) const{
                                            		return x==p.x && y==p.y && z==p.z;
                                            	}
                                            		bool operator != (const pa3 &p) const{
                                            			return !( x==p.x && y==p.y && z==p.z);
                                            	}
                                            
                                            };
                                            
                                            class pa4{
                                            	public:
                                            	double x;
                                            	int y,z,w;
                                            	pa4(double x=0,int y=0,int z=0,int w=0):x(x),y(y),z(z),w(w) {}
                                            	bool operator < (const pa4 &p) const{
                                            		if(x!=p.x) return x<p.x;
                                            		if(y!=p.y) return y<p.y;
                                            		if(z!=p.z)return z<p.z;
                                            		return w<p.w;
                                            		//return x != p.x ? x<p.x: y<p.y;
                                            	}
                                            	bool operator > (const pa4 &p) const{
                                            		if(x!=p.x) return x>p.x;
                                            		if(y!=p.y) return y>p.y;
                                            		if(z!=p.z)return z>p.z;
                                            		return w>p.w;
                                            		//return x != p.x ? x<p.x: y<p.y;
                                            	}
                                            	bool operator == (const pa4 &p) const{
                                            		return x==p.x && y==p.y && z==p.z &&w==p.w;
                                            	}
                                            		
                                            
                                            };
                                            class pa2{
                                            	public:
                                            	int x,y;
                                            	pa2(int x=0,int y=0):x(x),y(y) {}
                                            	pa2 operator + (pa2 p) {return pa2(x+p.x,y+p.y);}
                                            	pa2 operator - (pa2 p) {return pa2(x-p.x,y-p.y);}
                                            	bool operator < (const pa2 &p) const{
                                            		return y != p.y ? y<p.y: x<p.x;
                                            	}
                                            	bool operator > (const pa2 &p) const{
                                            		return x != p.x ? x<p.x: y<p.y;
                                            	}
                                            	bool operator == (const pa2 &p) const{
                                            		return abs(x-p.x)==0 && abs(y-p.y)==0;
                                            	}
                                            	bool operator != (const pa2 &p) const{
                                            		return !(abs(x-p.x)==0 && abs(y-p.y)==0);
                                            	}
                                            		
                                            
                                            };
                                            
                                                   #define ppa pair<int,pas>
                                            class Point{
                                            	public:
                                            	double x,y;
                                            	Point(double x=0,double y=0):x(x),y(y) {}
                                            	Point operator + (Point p) {return Point(x+p.x,y+p.y);}
                                            	Point operator - (Point p) {return Point(x-p.x,y-p.y);}
                                            	Point operator * (double a) {return Point(x*a,y*a);}
                                            	Point operator / (double a) {return Point(x/a,y/a);}
                                            	double absv() {return sqrt(norm());}
                                            	double norm() {return x*x+y*y;}
                                            	bool operator < (const Point &p) const{
                                            		return x != p.x ? x<p.x: y<p.y;
                                            	}
                                            	bool operator == (const Point &p) const{
                                            		return fabs(x-p.x)<EPS && fabs(y-p.y)<EPS;
                                            	}
                                            };
                                            typedef Point Vector;
                                     #define pl pair<int,pas>
                                            struct Segment{
                                            Point p1,p2;
                                            };
                                             double dot(Vector a,Vector b){
                                            	return a.x*b.x+a.y*b.y;
                                            }
                                            double cross(Vector a,Vector b){
                                            	return a.x*b.y-a.y*b.x;
                                            }
                                        
                bool parareru(Point a,Point b,Point c,Point d){
                //	if(abs(cross(a-b,d-c))<EPS)cout<<"dd "<<cross(a-b,d-c)<<endl;
                	return abs(cross(a-b,d-c))<EPS;
                }
                double distance_ls_p(Point a, Point b, Point c) {
                  if ( dot(b-a, c-a) < EPS ) return (c-a).absv();
                  if ( dot(a-b, c-b) < EPS ) return (c-b).absv();
                  return abs(cross(b-a, c-a)) / (b-a).absv();
                }
                bool is_intersected_ls(Segment a,Segment b) {
                	if(a.p1==b.p1||a.p2==b.p1||a.p1==b.p2||a.p2==b.p2) return false;
                	if(parareru((a.p2),(a.p1),(a.p1),(b.p2))&&parareru((a.p2),(a.p1),(a.p1),(b.p1))){
                //		cout<<"sss"<<endl;
                		if(dot(a.p1-b.p1,a.p1-b.p2)<EPS) return true;
                		if(dot(a.p2-b.p1,a.p2-b.p2)<EPS) return true;
                		if(dot(a.p1-b.p1,a.p2-b.p1)<EPS) return true;
                		if(dot(a.p1-b.p2,a.p2-b.p2)<EPS) return true;
                		return false;
                	}
                  else return ( cross(a.p2-a.p1, b.p1-a.p1) * cross(a.p2-a.p1, b.p2-a.p1) < EPS ) && ( cross(b.p2-b.p1, a.p1-b.p1) * cross(b.p2-b.p1, a.p2-b.p1) < EPS );
                }
                 
                double segment_dis(Segment a,Segment b){
                	if(is_intersected_ls(a,b))return 0;
                	double r=distance_ls_p(a.p1, a.p2, b.p1);
                	r=min(r,distance_ls_p(a.p1, a.p2, b.p2));
                	r=min(r,distance_ls_p(b.p1, b.p2, a.p2));
                	r=min(r,distance_ls_p(b.p1, b.p2, a.p1));
                	return r;
                }
                Point intersection_ls(Segment a, Segment b) {
                  Point ba = b.p2-b.p1;
                  double d1 = abs(cross(ba, a.p1-b.p1));
                  double d2 = abs(cross(ba, a.p2-b.p1));
                  double t = d1 / (d1 + d2);
                 
                  return a.p1 + (a.p2-a.p1) * t;
                }
                 
                                string itos( int i ) {
                                ostringstream s ;
                                s << i ;
                                return s.str() ;
                                }
                                 
                                int gcd(int v,int b){
                                	if(v>b) return gcd(b,v);
                                	if(v==b) return b;
                                	if(b%v==0) return v;
                                	return gcd(v,b%v);
                                }
                 
                                double distans(double x1,double y1,double x2,double y2){
                                	double rr=(x1-x2)*(x1-x2)+(y1-y2)*(y1-y2);
                                	return sqrt(rr);
                                	
                                }
                                int mod;
                                
                int pr[500010];
                int inv[500010];
                
                int beki(int wa,int rr,int warukazu){
                	if(rr==0) return 1%warukazu;
                	if(rr==1) return wa%warukazu;
                	if(rr%2==1) return (beki(wa,rr-1,warukazu)*wa)%warukazu;
                	int zx=beki(wa,rr/2,warukazu);
                	return (zx*zx)%warukazu;
                }
    double bekid(double w,int r){
    	if(r==0) return 1.0;
    	if(r==1) return w;
    	if(r%2) return bekid(w,r-1)*w;
    	double f=bekid(w,r/2);
    	return f*f;
    }
                
    			int comb(int nn,int rr){
    				int r=pr[nn]*inv[rr];
    				r%=mod;
    				r*=inv[nn-rr];
    				r%=mod;
    				return r;
    			}
                
                void gya(int ert){
                	pr[0]=1;
                	for(int i=1;i<ert;i++){
                		pr[i]=(pr[i-1]*i)%mod;
                	}
                	for(int i=0;i<ert;i++) inv[i]=beki(pr[i],mod-2,mod);
                	
                }
                
              //   cin.tie(0);
    		//	ios::sync_with_stdio(false);
    			//priority_queue<pa3,vector<pa3>,greater<pa3>> pq;            
                 //sort(ve.begin(),ve.end(),greater<int>());
                                         //----------------kokomade tenpure------------
                //vector<double> ans(100000000),ans2(100000000)

vector<int>G[400020];
int n,m;
int val[400010];
int sumi[400010];
queue<pa> qu;
/*
void ch(int r){
	for(int i=0;i<400010;i++)sumi[i]=inf;
	while(qu.size())qu.pop();
	for(int i=1;i<=n;i++)if(val[i]==r){
		qu.push(mp(2*i,0));
	}
	cout<<"r "<<endl;
	while(qu.size()){
		pa z=qu.front();
		qu.pop();
		if(sumi[z.first]<inf) continue;
		sumi[z.first]=z.second;
		for(auto v:G[z.first]){
			qu.push(mp(v,z.second+1));
		}
	}
	int am0=inf,bm0=inf,am1=inf,bm1=inf;
	for(int i=1;i<=n;i++){
		if(val[i]==r){
			am0=min(am0,sumi[i*2]);
			am1=min(am1,sumi[i*2+1]);
		}
		else{
			bm0=min(bm0,sumi[i*2]);
			bm1=min(bm1,sumi[i*2+1]);
		}
	}
	for(int i=1;i<=n;i++)cout<<sumi[2*i]<<" ";
	cout<<endl;
	
	for(int i=1;i<=n;i++)cout<<sumi[2*i+1]<<" ";
	cout<<endl;
	
	cout<<am0<<" "<<am1<<" "<<bm0<<" "<<bm1<<endl;
	if(am1>1 || bm0>2 || bm1>1) {
	cout<<"No"<<endl;
		exit(0);
	}
}
*/
/*
vector<int> kouho;
int cou[400010];
void ch(int r){
	//cout<<"d"<<endl;
	for(int i=0;i<400010;i++)sumi[i]=0,cou[i]=0;
	
	for(int i=1;i<=n;i++)if(val[i]==r){
		qu.push(mp(2*i,0));
	}
	for(int i=1;i<=n;i++){
		if(val[i]==r){
			for(auto v:G[2*i]) sumi[v/2]=1;
		}
	}
	for(int i=1;i<=n;i++)if(sumi[i]){
	//	cout<<i<<endl;
		for(auto v:G[2*i+1])if(val[v/2]!=r){
			if(val[i]==r)cou[v/2]|=2;
			else cou[v/2]|=1;
			
		}
	}
	for(int i=1;i<=n;i++)if(cou[i]==3){
		kouho.pb(i);
	//	cout<<i<<endl;
	}
	for(int i=0;i<400010;i++)sumi[i]=0,cou[i]=0;
	for(auto e:kouho){
		int i=e;
			for(auto v:G[2*i]) sumi[v/2]=1;
		
	}
	for(int i=1;i<=n;i++)if(sumi[i]){
		for(auto v:G[2*i+1])if(val[v/2]==r){
			if(val[i]==r)cou[v/2]|=2;
			else cou[v/2]|=1;
			
		}
	}
	int san=0;
for(int i=1;i<=n;i++)if(cou[i]==3)san++;
	if(san==0){
	cout<<"No"<<endl;
		exit(0);
	}

}
*/
int vis[400020]={0};
void dfs(int r){
	if(vis[r]==2) return;
	if(vis[r]==1){
		cout<<"Yes"<<endl;
		exit(0);
	}
	vis[r]=1;
	for(auto v:G[r])dfs(v);
	vis[r]=2;
}

    signed main(){
     
    	       cin.tie(0);
    			ios::sync_with_stdio(false);
cin>>n>>m;
    	string s;
    	cin>>s;
    	s="s"+s;
    	for(int i=1;i<=n;i++){
    		if(s[i]=='B')val[i]=1;
    		else val[i]=0;
    	}
    	int ab=0,aa=0,bb=0;
    	for(int i=0;i<m;i++){
    		int y,yy;
    		cin>>y>>yy;
    		if(val[y]+val[yy]==1)ab++;
    		else if(val[y]+val[yy]==2)bb++;
    		
    		else aa++;
    		if(val[y]!= val[yy]){
    	//	G[2*y].pb(2*yy+1);
    	//	G[2*yy].pb(2*y+1);
    		G[2*y+1].pb(2*yy);
    		G[2*yy+1].pb(2*y);
    		}
    		
    		if(val[y]==val[yy]){
    		G[2*y].pb(2*yy+1);
    		G[2*yy].pb(2*y+1);
    	//	G[2*y+1].pb(2*yy);
    	//	G[2*yy+1].pb(2*y);
    		}
    	}
    	if(aa==0||ab==0||bb==0){
    	cout<<"No"<<endl;
    		return 0;
    	}
    	for(int i=2;i<=2*n+1;i++)if(vis[i]==0)dfs(i);
    	
    	cout<<"No"<<endl;
  	return 0;
    }


Measured memory_bytes: 32700