var
//.....
i,k,n,s:integer;
a:array[1..200] of integer
//a - massiv,  n - razmer massiva  k - kol-vo elementov, vhodyashih v diapazon, s - summa etih elementov
//.....
begin
//zapolnaete massiv
for i:=1 to n do 
  if (a[i]>=-15)and(a[i]<=20) then 
  begin
    s:=s+a[i];
    k:=k+1;
  end;
if (k<>0) then  //proverka dlya predotvrasheniya deleniya na 0
writeln('sr arif = ',s/k)
else
writeln('v massive net udovletv elementov');
end.