1 //2014-01-21-14.47
  2 //2-SAT
  3 #include <iostream>
  4 #include <cstdio>
  5 #include <cstdlib>
  6 #include <cmath>
  7 #include <cstring>
  8 #include <algorithm>
  9 #include <queue>
 10 #include <stack>
 11 #include <vector>
 12 #define MP(a, b) make_pair(a, b)
 13 #define PB(a) push_back(a)
 14 
 15 using namespace std;
 16 
 17 typedef long long ll;
 18 typedef pair<int ,int> pii;
 19 typedef pair<unsigned int, unsigned int> puu;
 20 typedef pair<int ,double> pid;
 21 typedef pair<ll, int> pli;
 22 
 23 const int INF = 0x3f3f3f3f;
 24 const double eps = 1e-6;
 25 const int LEN = 1010;
 26 vector<int> Map[LEN];
 27 bool mark[LEN*2];
 28 int S[LEN*2], c;
 29 
 30 bool dfs(int x) {
 31     if(mark[x^1]) return false;
 32     if(mark[x]) return true;
 33     mark[x] = true;
 34     S[c++] = x;
 35     for(int i=0; i<Map[x].size(); i++)
 36         if(!dfs(Map[x][i])) return false;
 37     return true;
 38 }
 39 
 40 void init(int n){
 41     for(int i=0; i<n*2; i++)Map[i].clear();
 42     memset(mark, 0, sizeof mark);
 43 }
 44 
 45 void add_clause(int x, int xval, int y, int yval)
 46 {
 47     x = x*2 + xval;
 48     y = y*2 + yval;
 49     Map[x].PB(y);
 50 }
 51 
 52 bool solve(int n){
 53     for(int i=0; i<n*2; i+=2)
 54         if(!mark[i] && !mark[i+1]){
 55             c = 0;
 56             if(!dfs(i)) {
 57                 while(c > 0) mark[S[--c]] = false;
 58                 if(!dfs(i+1)) return false;
 59             }
 60         }
 61     return true;
 62 }
 63 
 64 int main()
 65 {
 66 //    freopen("in.txt", "r", stdin);
 67 
 68     int n, m, a, b, res;
 69     char op[11];
 70     while(scanf("%d%d", &n, &m)!=EOF){
 71         init(n);
 72         for(int i=0; i<m; i++){
 73             scanf("%d%d%d%s", &a, &b, &res, op);
 74             if(!strcmp(op, "AND") && res) {
 75                 add_clause(a, 0, a, 1);
 76                 add_clause(b, 0, b, 1);
 77             }else if(!strcmp(op, "AND") && !res){
 78                 add_clause(a, 1, b, 0);
 79                 add_clause(b, 1, a, 0);
 80             }else if(!strcmp(op, "XOR") && res){
 81                 add_clause(a, 0, b, 1);
 82                 add_clause(a, 1, b, 0);
 83                 add_clause(b, 0, a, 1);
 84                 add_clause(b, 1, a, 0);
 85             }else if(!strcmp(op, "XOR") && !res){
 86                 add_clause(a, 0, b, 0);
 87                 add_clause(a, 1, b, 1);
 88                 add_clause(b, 0, a, 0);
 89                 add_clause(b, 1, a, 1);
 90             }else if(!strcmp(op, "OR") && res){
 91                 add_clause(a, 0, b, 1);
 92                 add_clause(b, 0, a, 1);
 93             }else {
 94                 add_clause(a, 1, a, 0);
 95                 add_clause(b, 1, b, 0);
 96             }
 97         }
 98         if(solve(n)) printf("YES\n");
 99         else printf("NO\n");
100     }
101     return 0;
102 }