#include <iostream>
int main(){
	int D;
	std::cin>>D;
	int x=0,y=0,z=0,a;
	for(int i=0;i<=D;i++){std::cin>>a;x+=(i%2?-a:a);y+=a;z=a;}
	int b[3];b[0]=z;b[1]=(y-x)/2;b[2]=(x+y)/2-z;
	if(b[1]){
			if(b[2]){
				std::cout<<"2\n";
				std::cout<<b[2]<<" ";
			}else{
				std::cout<<"1\n";
			}
			std::cout<<b[1]<<" ";
		}else{
			std::cout<<"0\n";
		}
	std::cout<<b[0];
	return 0;
}