program suma_diagonala_sec;
type matrice = array[1..20,1..20] of integer;
var a:matrice;
i,j,s,n:integer;
begin
write('n=');readln(n);
for i:=1 to n do
for j:=1 to n do begin
write('a[',i,',',j,']=');readln(a[i,j]); end;
s:=0;
for i:=1 to n do
s:=s+a[i,n-i+1];
writeln('Suma elementelor sub diagonala secundara este:',s);
readln;
end.
