Program textu;
var i,k,j:integer;
    s,s1:string;
    t:set of char;
    f,g:text;

begin
assign(f, 'text.in'); reset(f);
assign(g, 'text.out'); rewrite(g);
j:=0; k:=0;
t:=['a'..'z', 'A'..'Z'];
repeat
readln(f,s1);
s:=s1+s;
until eof(f);
repeat
if not(s[1] in t) then delete(s,1,1);
until s[1] in t;
for i:=1 to length(s)-1 do
if not((s[i] in t)) and not((s[i+1] in t))  then
delete(s,i,1);
repeat
if s[1] in t then inc(j) else inc(k);
delete(s,1,1);
until length(s)=0;
if k=0 then k:=1;
writeln(g, j/k:0:0);
close(f); close(g);
end.