#include <fstream.h>
#include <iostream.h>

int n,k,c[11];
long long a,b;

ifstream salut("reguli.in");
ofstream   pa("reguli.out");

int main()
{
salut>>n>>a;
unsigned int i=0;
 int m=30 ;
while (m-1)  {  salut>>b; c[i]=b-a;i++;
		a=b;
		m--;
	     }

for (i = 1; i<10; i++) if (c[0]==c[i]) break;

k=i;

pa<<k<<endl;

for ( i=0; i<k; i++) pa<<c[i]<<endl;


return 0;
}