{
TASK: minjumps
LANG: PASCAL
}

program minjumps;
  var a,b,j,i,pom,c:integer;
      n:longint;


begin
  readln(a,b,n);
    if (n mod 2 = 1) and (a mod 2 = 0) and (b mod 2 = 0) then
      begin
        writeln('-1');
        exit;
      end;

    if (a<>1) and (n mod a = 0) then
      begin
        writeln (n div a);
        exit;
      end;
    if (b<>1) and (n mod b = 0) then
      begin
        writeln (n div b);
        exit;
      end;

  if n>100 then
    begin
      writeln('-1');
      exit;
    end;
  if (a=n) or (b=n) then
    begin
      writeln('1');
      exit;
    end;

  if a+b = n then
  begin
    writeln('2');
    exit;
  end;



  if (a=1) and (b<n) then
    begin
      for i:=1 to n do
        if b*i<n then
          j:=b*i
        else
          begin
            writeln((n-j)+i-1);
            exit;
          end;
     end;
  if (a=1) and (b>n) then
    begin
      writeln(n);
      exit;
    end;

  if a>b then
  begin
    pom:=b+n;
    c:=1;

    repeat
      begin
        if pom mod a = 0 then
          begin
            c:= pom div a;
            writeln(c+1);
            exit;
          end;
        if pom mod a <> 0 then
          begin
            inc(pom,a);
            inc(c);
          end;
       end;
    until pom>100;


  pom:=2*b + n ;
  c:=2;
   repeat
      begin
        if pom mod a = 0 then
          begin
            c:= pom div a;
            writeln(c+2);
            exit;
          end;
        if pom mod a <> 0 then
          begin
            inc(pom,a);
            inc(c);
          end;
       end;
    until pom>100;

   end;
  if b>a then
  begin
    pom:=a+n;
    c:=1;

    repeat
      begin
        if pom mod b = 0 then
          begin
            c:= pom div b;
            writeln(c+1);
            exit;
          end;
        if pom mod b <> 0 then
          begin
            inc(pom,b);
            inc(c);
          end;
       end;
    until pom>100;

  pom:=2*a + n;
  c:=2;

repeat
      begin
        if pom mod b = 0 then
          begin
            c:= pom div b;
            writeln(c+2);
            exit;
          end;
        if pom mod b <> 0 then
          begin
            inc(pom,b);
            inc(c);
          end;
       end;
    until pom>100;
  end;

  writeln('-1');






  end.