#include<iostream>
using namespace std;
int main(){
	int n,m,t,p,bt=0,bp=0;
	cin>>n>>m;
	while(cin>>t>>p){
		if(abs(p-bp)>t-bt)
			cout<<"No"<<endl,exit(0);
		bt=t,bp=p;
	}
	cout<<"Yes"<<endl;
}