const a=\a\, z='z', A=65,Z=91;
var c1,c2:char;
    i1,i2:integer;
    ordc1:integer;

begin
  write("Please input two letters: ");
  read(c1,c2);
  write("Please input two integers: ");
  read(i1,i2);
  if c1>=a then
    if c1<=z then
      begin
        ordc1 := c1-a+97;
        write("The ASCII of c1 is: ",ordc1)
      end
    else
      write("The letter you input is out of lowercase's range! ")
  else
    if c1<=Z then
      if c1>=A then     
        begin 
          ordc1 := c1-A+65;
          write("The ASCII of c1 is: ",ordc1)
        end
      else
        write("The letter you input is out of uppercase's range! ")
    else
      write("The letter you input is invalid! ");
  if c1<=c2 then
    r3:=(r1*i1+r2*i2-r1*i2-r2*i1)/(r1+r2)
  else
    r3:=(r1*i2+r2*i1-r1*i1-r2*i2)/(r1+r2);
  write("The result of arithmetic is: ",r3)
end.