program waterfire;
const
fin='goat.in';
fout='goat.out';
var
i,j,s,p,n,m,time:longint;
f,g:text;

Procedure Work;
var
ii,jj:longint;
Begin
while m<s do  begin
while n<p-5 do
  begin
     inc(n,5);
     inc(m,10);
     inc(time);
      if m>=s then exit;
  end;

   while p<=5 do
     begin
       if (p-n>2) then
         begin
          inc(n,2);
          inc(m,5);
          inc(time);
         end else
               if (p-n=2)and(s-m<=5) then
                 begin
                 inc(n,2);
                 inc(m,5);
                 inc(time);
                 end else
              begin
                  dec(n);
                  inc(m);
                  inc(time);
               end;
     if m>=s then exit;
     end;
                  if  (n=p-5)and(s-m<=10) then
                         begin
                            inc(n,5);
                            inc(m,10);
                            inc(time);
                         end else
                    if  (p-n<4)and(p-n>=2)and(s-m<=5) then
                         begin
                             inc(n,2);
                             inc(m,5);
                             inc(time);
                         end else begin
                                    dec(n,1);
                                    inc(m,1);
                                    inc(time);
                                  end;

     end;
End;
BEGIN
n:=0;m:=0;time:=0;
assign(f,fin);reset(f);
assign(g,fout);rewrite(g);
read(f,s,p);
work;
writeln(g,time);
close(f);close(g);
END.