Find the sum of the elements in a one-dimensional array ending in 3 and in even places. Pascal program

Const n = 10;
var i, s: integer;
a: array [1..n] of integer;
begin
for i: = 1 to n do begin
a [i]: = random (20);
write (a [i], ”);
end;
for i: = 1 to n do begin
if (i mod 2 = 0) then begin {check parity}
if (a [i] mod 10 = 3) then {here we check that the number ends in 3} s: = s + a [i];
end;
writeln;
write (‘summa =’, s);
end.