#include<iostream>
#include<map>
#include<string>
#include<cstring>
#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<queue>
#include<vector>
#include<algorithm>
using namespace std;
const int MAXN = 1010;  
struct twosat  
{    
    int n,c;    
    vector<int> g[MAXN<<1];    
    bool mark[MAXN<<1];    
    int s[MAXN<<1];    
      
    bool dfs(int x)   
    {    
        int i;  
        if (mark[x^1])   
            return 0;    
        if (mark[x])   
            return 1;    
        mark[x] = 1;    
        s[c++] = x;    
        for (i = 0; i < g[x].size(); i++)    
            if (!dfs(g[x][i]))   
                return 0;    
        return 1;    
    }    
      
    void init(int n)   
    {    
        int i,t=n<<1;  
        this->n = n;    
        for (i = 0; i < t; i++)     
            g[i].clear();    
        memset(mark, 0, sizeof(mark));    
    }    
    
    void add_clause(int x,int xval,int y,int yval)   
    {    
    	x=x*2+xval;
    	y=y*2+yval;
        g[x].push_back(y^1);    
        g[y].push_back(x^1);  
    }    
    
    bool solve()   
    {    
        int i,t=n<<1;  
        for (i = 0; i < t; i += 2)     
            if (!mark[i] && !mark[i + 1])   
            {    
                c = 0;    
                if (!dfs(i))   
                {    
                    while (c > 0)   
                        mark[s[--c]] =0;     
                    if (!dfs(i + 1))   
                        return 0;    
                }    
            }  
        return 1;    
    }    
}ender;
int work(int a,int b,int k)
{
	return k==0?a&b:k==1?a|b:a^b;
}
int main()
{
	char s[100];
	int a,b,c,n,m,x,y,k;
	while(cin>>n>>m)
	{
		ender.init(n);
		while(m--)
		{
			scanf("%d%d%d%s",&a,&b,&c,s);
			k=strcmp(s,"AND")==0?0:strcmp(s,"OR")==0?1:2;
			for(x=0;x<2;x++)
				for(y=0;y<2;y++)
					if(work(x,y,k)!=c)
						ender.add_clause(a,x,b,y);
		}
		cout<<(ender.solve()?"YES":"NO")<<endl;
		
	}
	return 0;
}

The first line contains two integers N (1 ≤ N ≤ 1000) and M,(0 ≤ M ≤ 1,000,000) indicating the number of vertices and edges.
The following M lines contain three integers a (0 ≤ a <N), b(0 ≤ b < N), c and an operator op each, describing the edges.

Output a line containing "YES" or "NO".