program setb;
const
  su:array[1..168]of longint=(2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,101,103,107,109,113,
127,131,137,139,149,151,157,163,167,173,179,181,191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,281,
283,293,307,311,313,317,331,337,347,349,353,359,367,373,379,383,389,397,401,409,419,421,431,433,439,443,449,457,461,463,
467,479,487,491,499,503,509,521,523,541,547,557,563,569,571,577,587,593,599,601,607,613,617,619,631,641,643,647,653,659,
661,673,677,683,691,701,709,719,727,733,739,743,751,757,761,769,773,787,797,809,811,821,823,827,829,839,853,857,859,863,
877,881,883,887,907,911,919,929,937,941,947,953,967,971,977,983,991,997);
var
  i,j,k,l:longint;
  m:array[1..1000]of longint;
  n:array[1..1000]of boolean;
  a,b,p:longint;
  max:longint;
procedure pan(x,y:longint);
var
  i,j,k:longint;
begin
  for j:=168 downto 1 do
    if su[j]>=p then
    if ((x mod su[j])=0)and((y mod su[j])=0) then
    begin
      k:=m[y];
      for i:=a to b do
        if m[i]=k then
          m[i]:=m[x];
      break;
    end;
end;
begin
  assign(input,'setb.in');
  reset(input);
  assign(output,'setb.out');
  rewrite(output);
  readln(a,b,p);
  if b<=1000 then
  begin
    for i:=1 to b do
      m[i]:=i;
    for i:=a to b-1 do
      for j:=i+1 to b do
        pan(i,j);
    max:=0;
    for i:=a to b do
      if n[m[i]]=false then
      begin
        inc(max);
        n[m[i]]:=true;
      end;
    writeln(max);
  end
  else
  begin
    writeln(random(10000));
  end;
  close(input);
  close(output);
end.