program cifra;
var t:array[1..100]of 0..9;
    cit:string;
    n,i,j,s,l,k,l1,c:longint;
    f,g:text;

procedure lucru;
begin
s:=0;
read(f,n);
for j:=1 to n do
  begin
    l:=j;
    l1:=j;
    for k:=2 to (j mod 10) do
      l:=((l mod 10)*(l1 mod 10))mod 10;
    inc(s,l);
    s:=s mod 10;
  end;
writeln(g,s);
end;

procedure back(var c:longint;cit:string);
var j:longint;
begin
if c<length(cit) then
for j:=1 to 10 do
  begin
    inc(c);
    lucru;
    back(c,cit);
  end;
end;

begin
assign(f,'cifra.in');
reset(f);
assign(g,'cifra.out');
rewrite(g);
read(f,cit);
for i:=1 to length(cit) do
    if cit[i]='0' then t[i]:=0
                  else
    if cit[i]='1' then t[i]:=1
                  else
    if cit[i]='2' then t[i]:=2
                  else
    if cit[i]='3' then t[i]:=3
                  else
    if cit[i]='4' then t[i]:=4
                  else
    if cit[i]='5' then t[i]:=5
                  else
    if cit[i]='6' then t[i]:=6
                  else
    if cit[i]='7' then t[i]:=7
                  else
    if cit[i]='8' then t[i]:=8
                  else
    if cit[i]='9' then t[i]:=9;
c:=1;
for i:=1 to length(cit) do
  for i:=1 to t[i] do
    if length(cit)>1 then back(c,cit)
                     else lucru;
close(f);
close(g);
end.