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

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

typedef unsigned long ulong;

void radix_sort_aux(ulong*a,ulong*b,int n){
	int c[1024];
	for(int i=0;i<1024;++i){
		c[i]=0;
	}
	for(int i=0;i<n;++i){
		++c[a[i]&1023];
	}
	int t=0;
	for(int i=0;i<1024;++i){
		int u=c[i];
		c[i]=t;
		t+=u;
	}
	for(int i=0;i<n;++i){
		b[c[a[i]&1023]++]=a[i]>>10|a[i]<<54;
	}
}

void radix_sort(ulong*a,int n){
	static ulong b[100000];
	radix_sort_aux(a,b,n);
	radix_sort_aux(b,a,n);
	radix_sort_aux(a,b,n);
	for(int i=0;i<n;++i){
		a[i]=b[i]>>34|b[i]<<30;
	}
}

typedef struct { unsigned b,a; } AB;
AB ab[100000];

int main(){
	char*mmap();
	char*rp=mmap(0l,1l<<25,1,2,0,0ll);
	long n=rd();
	long m=rd();
	rep(i,m){
		ab[i].a=rd();
		ab[i].b=rd();
	}
	radix_sort(ab,m);
	long z=n*2-2;
	long c=0;
	rep(i,m){
		if(!(ab[i].a<c)){
			--z;
			c=ab[i].b;
		}
	}

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