uses crt;
var f:text; s:string; n,i,t,tong:longint;
begin
clrscr;
assign(f,'TIMSO.INP'); reset(f);
readln(f,s);
close(f);
assign(f,'TIMSO.OUT'); rewrite(f);
val(s,n);
while n<>0 do
begin
inc(t,n mod 10);
n:=n div 10;
end;
while t<>0 do
begin
inc(tong,t mod 10);
t:=t div 10;
end;
writeln(f,tong);
close(f);
readln
end.