var
a:char;
begin
readln(a);
if (ord(a)>=65)and(ord(a)<=90) then
writeln(chr(ord(a)+32))
else
if (ord(a)>=97)and(ord(a)<=122) then
writeln(chr(ord(a)-32))
else
writeln(a);
end.
C語言
void main()
{
char a;
scanf("%c",&a);
if ((a>=65)&&(a<=90))
printf("%c",a+32);
else if ((a>=97)&&(a<=122))
printf("%c",a-32);
else
printf("%c",a);
}