uses crt;
var a,b,c:char;
begin
clrscr;
repeat
b:=a;
a:=readkey;
if (a>='a')and(a<='z') then c:=b;
write(a);
until a='.';
writeln;
write(c);
end.
Вариант 2
program lab3;
uses crt;
var a,b,c:char;
begin
readln(a);
while a<>'.' do
begin
b:=a;
readln(a);
if (a>='a') and (a<='z') then
c:=b;
end;
write('symbol is ',c);
end.