{
TASK:minjumps
LANG:PASCAL
}
var
 n,a,b,c,p,cnt1,cnt2,cnt,cn,q:integer;
begin
 readln(a,b,n);
 if a<b then begin c:=b; b:=a; a:=c; end;
 if n mod a=0 then begin writeln(n div a); halt(0); end;
 p:=0;
 cnt1:=0;
 repeat
  p:=p+b;
  inc(cnt1);
  cnt:=(n-p) div a;
  if cnt<0 then cnt:=cnt*-1;
  if ((n-p) mod a=0) then begin
                           cnt1:=cnt1+cnt;
                           break;
                          end;
 until p>10000;
 q:=0;
 cnt2:=0;
 repeat
  q:=q-b;
  inc(cnt2);
  cnt:=(n-q) div a;
  if cnt<0 then cnt:=cnt*-1;
  if ((n-q) mod a=0) then begin
                           cnt2:=cnt2+cnt;
                           break;
                          end;
 until q<-10000;
 if(q>=-10000)and(p<=10000) then begin
                                  if cnt1>cnt2 then cnt1:=cnt2;
                                  writeln(cnt1);
                                  halt(0);
                                 end;
 writeln(-1)
end.