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

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

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

int main()
{
salut>>n>>a;
long i=0,k=0;
int m=30
while (m)  {  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;
}