#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

char*mmap();

#define rd(v) long v=0;{long _c;while(_c=*rp++-48,_c>=0)v=v*10+_c;}
#define wt(v) {long _z=v;do*--wp=_z%10+48;while(_z/=10);}
#define rep(v,e) for(long v=0;v<e;++v)
#define chmax(v,a) (v=v>=a?v:a)

short d[1001][1001];

void f11(char*rp,long n,long m){
	rd(q);
	rep(i,q){
		rd(a);
		rd(b);
		d[a][b]=1;
	}
}

long f12(){
	rep(x,1000){
		rep(y,1000){
			long t=d[x][y]+d[x+1][y+1];
			chmax(t,d[x][y+1]);
			chmax(t,d[x+1][y]);
			d[x+1][y+1]=t;
		}
	}
}

long f1(){
	char*rp=mmap(0l,1l<<25,1,2,0,0ll);
	rd(n);
	rd(m);
	f11(rp,n,m);
	f12();
	return d[n][m];
}

void f2(long z){
	char wbuf[64],*wp=wbuf+sizeof wbuf;
	wt(z);
	write(1,wp,wbuf+sizeof wbuf-wp);
	_exit(0);
}

main(){
	f2(f1());
}