var
i, n, r: integer;
a: array [1 .. 100] of integer;
begin
write('Введите размер массива=');
readln(n);
writeln('Массив');
randomize;
for i := 1 to n do
begin
a[i] := random(51);
write(a[i], ' ');
end;
i := 0;
writeln;
writeln('Итоговый массив');
while (i < n) do
begin
inc(i, 2);
r := a[i];
a[i] := a[i - 1];
a[i - 1] := r;
end;
for i := 1 to n do
write(a[i], ' ');
readln
end.