#include<stdio.h>
long long int x,i,c[500011],l,p,ant,n;
int main(){
FILE *f=fopen("reguli.in","r");
fscanf(f,"%lld %lld %lld",&n,&ant,&x);
c[1]=x-ant;
l=1;p=1;
ant=x;
for(i=3;i<=n;i++)
        {fscanf(f,"%lld",&x);
         p++;
         c[p]=x-ant;
         if(c[p]!=c[p-l])
         {if(c[p]==c[1])
                l=p-1;
         else
                l=p;}
        ant=x;
        }
fclose(f);
FILE *g=fopen("reguli.out","w");
fprintf(g,"%lld\n",l);
for(i=1;i<=l;i++)
        fprintf(g,"%lld\n",c[i]);
fclose(g);
return 0;}