#include using namespace std; #ifdef LOCAL_DEBUG #include "LOCAL_DEBUG.hpp" #endif #define int long long const int MOD = 1e9 + 7; struct Combination{ const int MOD = 1e9+7; vector fact; // fact[i] = iの階乗 void init(int n){ fact.resize(n+1); fact[0] = fact[1] = 1; for(int i = 2; i <= n; i++){ fact[i] = i * fact[i-1] % MOD; } } int nCr(int n,int r){ // nCr = n!/r!(n-r)! return fact[n] * mod_pow(fact[r]*fact[n-r]%MOD,MOD-2,MOD) % MOD; } int mod_pow(int n,int p,int MOD){ // a/n ≡ a*n^(p-2) nとpは互いに素 int r = 1; for(; p > 0; p >>= 1){ if(p & 1LL) r = (r * n) % MOD; n = (n * n) % MOD; } return r; // r = n^p % MOD } }comb; signed main(){ int n; cin >> n; vector a(n); for(int i = 0; i < n; i++){ cin >> a[i]; } int ans = 0; comb.init(100001); for(int i = 0; i < n; i++){ ans = (ans + a[i] * comb.nCr(n-1, i)) % MOD; } cout << ans << endl; return 0; }