var a,b,ct,S:longint;
    c,i,c1:char;
    f,g:text;
    m:set of char;
begin
assign(f,'text.in'); reset(f);
m:=[];
for i:='a' to 'z' do
m:=m+[i];
while (not eoln(f)) do
begin
read(f,c1);
if [c1]*m<>[] then begin inc(ct);
                        if [c]*m=[] then S:=S+1;
                        end;
c:=c1;
end;
close(f);
assign(g,'text.out'); rewrite(g);
writeln(g,ct div s);
close(g);
end.