program dayXenKe;
uses crt;
var a: array[1..20] of byte;
n, i, j: byte;
kt: boolean;
begin
clrscr; kt:=true;
write('n = '); readln(n);
for i:= 1 to n do
begin
write('a[',i,'] = '); readln(a[i]);
if (a[i]>1) or (a[i]<0) then
begin
kt:=false; break;
end;
end;
i:=3; j:=4;
while (i<=n) and(j<=n) do
begin
if (a[i]<>a[1]) or (a[j]<>a[2]) then
begin
kt:=false; break;
end
else
begin
i:=i+2; j:=j+2;
end;
end;
if kt=true then write('co')
else write('khong');
readln;
end.
