program goat;
const
max=1000000;
type
fa=record
ss:longint;
pp:integer;
t:longint;
fb:longint;
end;
sz=array[1..max]of fa;
const
f:array[1..3]of fa=((ss:-1;pp:1),(ss:-5;pp:-2),(ss:-10;pp:-5));
var
f1,f2:text;
s:longint;
p:integer;
a:sz;
h,t:longint;
procedure ini;
var
i:longint;
begin
assign(f1,'goat.in');reset(f1);
assign(f2,'goat.out');rewrite(f2);
read(f1,s,p);
close(f1);
for i:=1 to max do begin a[i].ss:=-1;a[i].pp:=-1;a[i].t:=0;a[i].fb:=0;end;
a[1].ss:=s;
a[1].pp:=p;
h:=0;t:=1;
end;
function pan(s:longint;p:integer;t:longint):boolean;
var
i:longint;
k:boolean;
begin
k:=false;
i:=h;
if p<0 then k:=true;
while (k=false)and(i<t)do begin
if (s=a[i].ss)and(p=a[i].pp)and(t=a[i].t)then k:=true;
inc(i);
end;
pan:=k;
end;
procedure dfs;
var
i:integer;
begin
repeat
inc(h);
if a[h].ss<=0 then exit
else begin
if a[h].pp >0 then begin
for i:=1 to 3 do begin
inc(t);
a[t].ss:=a[h].ss+f[i].ss;
if a[h].pp+f[i].pp<=p then a[t].pp:=a[h].pp+f[i].pp
else a[t].pp:=a[h].pp;
a[t].t:=a[h].t+1;
a[t].fb:=h;
if pan(a[t].ss,a[t].pp,a[t].t) then dec(t);
end;
end;
end;
until t=max;
end;
begin
ini;
dfs;
write(f2,a[h].t);
close(f2);
end.
zhai