#include using namespace std; using ll=long long; #define rep2(i, a, n) for(int i = (a); i < (n); i++) #define rep(i, n) rep2(i,0,n) void in(){} template void in(Head&& head,Tail&&... tail){cin>>head;in(forward(tail)...);} int main(){ cin.tie(nullptr);ios_base::sync_with_stdio(false); int a,b,c,d; in(a,b,c,d); if(a>c){ cout<<"null"<d&&b!=2&&d!=0){ cout<<"null"<