const nmax=15;
type matr=array[1..nmax,1..nmax] of integer;
procedure Summa(m:matr;n:byte;var s:integer);
var i:byte;
begin
s:=0;
for i:=1 to n do
s:=s+m[i,i];
end;
var a:matr;
n:byte;
sum,i,j:integer;
begin
randomize;
write('enter n: ');
readln(n);
for i:=1 to n do begin
for j:=1 to n do begin
a[i,j]:=random(50);
write(a[i,j]:4);
end;
writeln;
end;
summa(a,n,sum);
write('Summa=',sum);
readln
end.