#include<bits/stdc++.h>
#define For(i,j,k) for(int i=(j);i<=(k);++i)
#define ForDown(i,j,k) for(int i=(j);i>=(k);--i)
#define Debug(fmt, args...) fprintf(stderr,"(func %s, line #%d): " fmt,__func__,__LINE__,##args),fflush(stderr)
#define debug(fmt, args...) fprintf(stderr,fmt,##args),fflush(stderr)
#define within :
#define LJY main
using namespace std;
typedef long long ll;
const int N=1e5+5;
mt19937 rnd(chrono::system_clock::now().time_since_epoch().count());
inline int read(){
  char ch=getchar();int x=0,f=1;
  while(ch<'0'||ch>'9'){if(ch=='-') f=-1;ch=getchar();}
  while(ch>='0'&&ch<='9')
    x=(x<<3)+(x<<1)+(ch^48),ch=getchar();
  return x*f;
}
int n,m;
vector<int>G[N<<1];
int low[N],dfn[N],cdfn,stk[N],tp;bool vis[N];
int bel[N],scc;
void tarjan(int u){
  dfn[u]=low[u]=++cdfn;stk[++tp]=u;vis[u]=1;
  for(int v within G[u])
    if(!dfn[v]) tarjan(v),low[u]=min(low[u],low[v]);
    else if(vis[v]) low[u]=min(low[u],dfn[v]);
  if(low[u]==dfn[u]){
    int y;++scc;
    while(y=stk[tp--]){
      bel[y]=scc;vis[y]=0;
      if(y==u) break;
    }
  }
}
void dfs(int u){vis[u]=1;for(int v within G[u]) if(!vis[v]) dfs(v);}
void ljy(){
  For(i,1,(n<<1)|1) G[i].clear();
  For(i,1,m){
    int u=read(),v=read();
    if(u>0) u=u<<1;else u=(-u)<<1|1;
    if(v>0) v=v<<1;else v=(-v)<<1|1;
    G[u^1].emplace_back(v);G[v^1].emplace_back(u);
  }memset(dfn,0,sizeof(dfn));memset(vis,0,sizeof(vis));cdfn=scc=0;
  For(i,2,(n<<1|1)) if(!dfn[i]) tarjan(i);
  For(i,1,n) if(bel[i<<1]==bel[i<<1|1]){puts("no");return;}
  dfs(2);For(i,1,n) if(vis[i<<1]&&vis[i<<1|1]){puts("no");return;}
  puts("yes");
}
signed LJY(){while(scanf("%d%d",&n,&m)==2) ljy();}