1 #include <iostream> 2 #include <algorithm> 3 #include <string> 4 5 #define MOD 1000000007 6 using namespace std; 7 8 long long quick_pow(long long a, long long b, long long c){ 9 long long ans = 1; 10 a = a%c; 11 while (b > 0){ 12 if (b % 2 == 1){ 13 ans = (ans*a) % c; 14 } 15 b = b / 2; 16 a = (a*a) % c; 17 } 18 return ans; 19 } 20 21 int main(){ 22 ios::sync_with_stdio(false); 23 /* 24 freopen("in.txt", "r", stdin); 25 freopen("out.txt", "w", stdout); 26 */ 27 long long x; 28 while (cin >> x){ 29 x++; 30 long long ans = quick_pow(3, x, MOD); 31 ans--; 32 ans = ans * 500000004 % MOD; 33 cout << ans << endl; 34 } 35 //fclose(stdin); 36 //fclose(stdout); 37 //system("pause"); 38 return 0; 39 }