program cojs_p487;
var
	jud:array[0..100000] of boolean;
	e:array[0..10000] of longint;
	q,head,next,v:array[0..100000] of longint;
	p,a,b,i,j,k,tot,sum,x,num,s0,he,ta,y:longint;
	flag:boolean;
procedure eratos;
var
    i,j:longint;
begin
    jud[1]:=false;
    for i:=2 to b do
		jud[i]:=true;
    for i:=2 to b div 2 do
        if jud[i]
		then begin
			for j:=2 to b div i do
				jud[i*j]:=false;
			if i>=p
			then begin
				inc(num);
				e[num]:=i;
			end;
		end;
end;
procedure ass;
begin
	assign(input,'setb.in');
	assign(output,'setb.out');
	reset(input);
	rewrite(output);
end;
procedure cls;
begin
	close(input);
	close(output);
end;
procedure add(x,y:longint);
begin
	inc(tot);
	v[tot]:=y;
	next[tot]:=head[x];
	head[x]:=tot;
end;
procedure init;
begin
	ass;
	readln(a,b,p);
	eratos;
	sum:=b-a+1;
	fillchar(jud,sizeof(jud),true);
	for i:=a to b do
		for j:=1 to num do
			if (i mod e[j]=0) and jud[e[j]]
			then begin
				jud[e[j]]:=false;
				if a mod e[j]=0
					then x:=a div e[j]
					else x:=(a div e[j])+1;
				for k:=x to b div e[j] do
                                begin
					add(i,k*e[j]);
                                        add(k*e[j],i);
                                end;
			end;
end;
begin
	init;
	fillchar(jud,sizeof(jud),false);
	s0:=sum;
	while s0>0 do
	begin
		he:=0;ta:=1;
		for i:=a to b do
			if not(jud[i]) then begin q[ta]:=i; jud[i]:=true; dec(s0); break; end;
			while he<ta do
			begin
				inc(he);
				x:=q[he];
				k:=head[x];
				y:=v[k];
				while k<>0 do
				begin
					if not(jud[y]) then begin inc(ta); q[ta]:=y; jud[y]:=true; dec(s0); dec(sum); end;
					k:=next[k];
					y:=v[k];
				end;
			end;
	end;
	writeln(sum);
	cls;
end.