uses crt;
const nmax=20;
var a:array[1..nmax,1..nmax] of integer;
n,i,j,k,k1:byte;
sm:integer;
begin
clrscr;
randomize;
repeat
write('Размер матрицы=');
readln(n);
until n in [1..nmax];
writeln('Исходная матрица:');
for i:=1 to n do
begin
for j:=1 to n do
begin
a[i,j]:=random(10)-1;
write(a[i,j]:4);
end;
writeln;
end;
writeln;
sm:=0;
for j:=1 to n do
begin
k:=0;
for i:=1 to n do
if a[i,j]<0 then k:=1;
if k=0 then
for i:=1 to n do
sm:=sm+a[i,j]
else break;
end;
write('Сумма элементов столбцов до первого столбца с отрицательным=',sm);
readln
end.