Сложение двух столбцов в двумерном массиве

for i:=1 to n do
   for j:=1 to m do
    sum:=a[i,st1]+a[i,st2]);

Program Pro_957;
  Uses crt;
  var a: array[1..3,1..3] of integer;
  i,j,q,s,sum: integer;
begin clrscr;
  for i:=1 to 3 do
  for j:=1 to 3 do begin
  writeln(' vvedite  ',j,' element  ',i,' stroki');
  readln(a[i,j]);
end;
  for i:=1 to 3 do begin
  for j:=1 to 3 do
  write(a[i,j]:3);
writeln;
end;
writeln;
  for i:=1 to 3 do
  for j:=1 to 3 do begin
sum:=(a[i,1]+a[i,2]);
end;
writeln('summa:',sum);
 
 
readln;
end.

Program Pro_957;
  Uses crt;
  var a: array[1..3,1..3] of integer;
  i,j,q,s,sum: integer;
begin clrscr;
  for i:=1 to 3 do
  for j:=1 to 3 do begin
  writeln(' vvedite  ',j,' element  ',i,' stroki');
  readln(a[i,j]);
end;
  for i:=1 to 3 do begin
  for j:=1 to 3 do
  write(a[i,j]:3);
writeln;
end;
writeln;
for i:=1 to 3 do
sum:=sum+a[i,1]+a[i,2];
writeln('summa:',sum);
readln;
end.

Program Pro_957;
Uses crt;
var
  a: array[1..100,1..100] of integer;
  i,j,q,s,sum,n,m: integer;
begin
  clrscr;
  randomize;
  write('n=');
  read(n);
  write('m=');
  read(m);
  for i:=1 to n do
  for j:=1 to m do
   a[i,j]:=random(50);
  for i:=1 to n do
   begin
      for j:=1 to m do
       write(a[i,j],'  ');
      writeln;
   end;
  writeln;
  write('q=');
  read(q);
  write('s=');
  read(s);
  if (q>m)or(s>m) then writeln('Oshibka! Prevyshenie kol-va stolbcov')
  else
   begin
      for i:=1 to n do
      for j:=1 to m do
       begin
          sum:=0;
          sum:=(a[i,q]+a[i,s]);
          write('a[',i,',',q,']+','a[',i,',',s,']=',sum);
          writeln;
       end;
   end;
  readln;
end.