-

Good point. But for training neural network you can generate more samples by adding some random noise to the samples.

void solve(int m)
{
	vector<int> g(m);
	for (int i = 0; i < m; i++) {
		read_int(&g[i]);
	}
	for (int i = 0; i < m; i++) {
		if (g[i] % g[0] != 0) {
			write_int_n(-1);
			return;
		}
	}
	write_int_n(m * 2);
	for (auto o : g) {
		write_int_s(o);
		write_int_s(g[0]);
	}
	putchar('\n');
}

smallest element of set is already present in the set :D

and she/he must check if the answer exists or not (she/he asked why original set is not valid)

and if answer exists the gcd of all elements is the smallest element of set

Hi consider this case:

3
1 9 15

gcd(9, 15) => 3

but 3 is not exists in input set.

He remembered that he calculated gcd(ai, ai + 1, ..., aj) for every 1 ≤ i ≤ j ≤ n and put it into a set S.

to overcome this problem we can insert smallest value from set between each of two elements.

so the answer would be:

6
1 1 9 1 15 1

You have to remove the minimum possible number of consecutive ( standing one after another ) characters from string b

http://ideone.com/n1Pr3O