Вматрице a(3,5) найти сумму элементов

Var a:array [1..3,1..5] of integer;
i,j,s:integer;
begin
randomize;
for i:=1 to 3 do begin
for j:=1 to 5 do begin
a[i,j]:=random(21)-10;
write (a[i,j]:4);
end;
writeln;
end;
for i:=1 to 3 do
for j:=1 to 5 do
s:=s+a[i,j];
writeln (s);
readln;
end.