#include<iostream>
#include<fstream>
using namespace std;
ifstream f("sume.in");
ofstream g("sume.out");
int i,x,n,v[30000],y,z,t,r,a;
int main()
{
f>>n;
for(i=1;i<=n;i++)
f>>v;
x=n;
while(x!=0)
{r++;
x=x-r;}
r=r+1;
if(x<0)
g<<-1;
else
{y=v[1];
z=v[r];
t=v[2];
t=t-z;
a=y+t;
a=a/2;
g<<r<<'\n'<<a<<" ";
for(i=1;i<=r-1;i++)
g<<v-a<<" ";}}
stie cineva de ce iau 0 ..pe exemplu merge