#include <fstream>
#include <math.h>
using namespace std;
 
int main()
{        int n,nr,i, a[25004], s[25004], sumain=0, sumaout=0;
ifstream fin("sume.in");
ofstream fout("sume.out");
fin>>nr;
n=(1+(int)sqrt(1+8*nr))/2;
 
for(i=1;i<=n;i++)
{fin>>s[i];
sumain+=s[i];
}
 
a[1]=(s[1]+s[2]-s[n])/2;//s[1]= primul+al doilea
//s[2]=primul +al treilea=
//s[n]= al doilea +al treilea
sumaout=sumaout+a[1];
for(i=1;i<=n-1;i++)
sumaout=sumaout+(s[i]-a[1]);
if (sumaout%sumain!=0) 
{fout<<n<<"\n";
fout<<a[1]<<" ";
for(i=1;i<=n-1;i++)
fout<<(s[i]-a[1])<<" ";
}
else
fout<<"-1\n";

return 0;
}