#include using namespace std; typedef long long ll; typedef pair p_ll; template void debug(T itr1, T itr2) { auto now = itr1; while(now=0; i--) const ll MOD = pow(10,9)+7; const ll LLINF = pow(2,61)-1; const int INF = pow(2,30)-1; vector fac; void c_fac(int x=pow(10,6)+10) { fac.resize(x,true); rep(i,x) fac[i] = i ? (fac[i-1]*i)%MOD : 1; } ll inv(ll a, ll m=MOD) { ll b = m, x = 1, y = 0; while (b!=0) { int d = a/b; a -= b*d; swap(a,b); x -= y*d; swap(x,y); } return (x+m)%m; } ll nck(ll n, ll k) { return fac[n]*inv(fac[k]*fac[n-k]%MOD)%MOD; } ll gcd(ll a, ll b) { if (a> N; ll T[N]; rep(i,N) cin >> T[i]; vector v = {0,2,4,5,7,9,11}; vector cand; rep(i,12) { bool used[12] = {}, ok = true; for (auto x: v) used[(i+x)%12] = true; rep(i,N) ok &= used[T[i]]; if (ok) cand.push_back(i); } ll result = cand.size()==1 ? cand[0] : -1; cout << result << endl; return 0; }