#define _USE_MATH_DEFINES #include "bits/stdc++.h" using namespace std; #define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i)) #define rep(i,j) FOR(i,0,j) #define each(x,y) for(auto &(x):(y)) #define mp make_pair #define MT make_tuple #define all(x) (x).begin(),(x).end() #define debug(x) cout<<#x<<": "<<(x)<; using vi = vector; using vll = vector; int R[4] = { 0,1, 4, 729 }; void solve() { const int P = (int)1e9 + 7; int N; cin >> N; vi A(N); rep(i, N) { cin >> A[i]; if (A[i] == 0) { cout << -1 << endl; return; } } ll S = 1; rep(i, N) { if (A[i] > 3 || (S *= R[A[i]]) > P) { cout << P << endl; return; } } cout << P % S << endl; } int main() { ios::sync_with_stdio(false); cin.tie(0); cout << fixed << setprecision(15); solve(); return 0; }