priority_queue<pair<ll,ll>> q;

ll bs[1d5];
ll ad,as[1d5+1];

{
	int @n,@m;
	rd(bs(n));
	rep(m){
		ll @l,@r;
		q.push({-(l-1),-(r)});
	}
	rep(i,0,n,2)bs[i]=-bs[i];
	int x=0;
	while(!q.empty()){
		pair<ll,ll> p=q.top();
		q.pop();
		ll l=-p.first;
		ll r=-p.second;
		while(x<l){
			ad+=as[x];
			if(bs[x]!=ad){
				wt("NO");
				exit(0);
			}
			++x;
		}
		while(!q.empty()&&-q.top().first==l){
			pair<ll,ll> p2=q.top();
			q.pop();
			q.push({-r,-p2.second});
		}
		ad+=as[x];
		as[r]-=bs[x]-ad;
		ad=bs[x];
		++x;
	}
	{
		while(x<n){
			ad+=as[x];
			if(bs[x]!=ad){
				wt("NO");
				exit(0);
			}
			++x;
		}
	}
	wt("YES");
}