#include #include #define MAT_ORDER 3 #define MOD 1000000007 typedef long long sqmat_t[MAT_ORDER][MAT_ORDER]; void multiSqMat(sqmat_t Z, const sqmat_t X, const sqmat_t Y) { int i, j, k; for (i = 0; i < MAT_ORDER; i++) for (j = 0; j < MAT_ORDER; j++) { Z[i][j] = 0; for (k = 0; k < MAT_ORDER; k++) { Z[i][j] += X[i][k] * Y[k][j]; Z[i][j] %= MOD; } } } void fastPowMat(sqmat_t Y, const sqmat_t X, long long n) { int i; sqmat_t tmp; sqmat_t XX, prod = {0}; memcpy(XX, X, sizeof(sqmat_t)); for (i = 0; i < MAT_ORDER; i++) prod[i][i] = 1; while (n) { if (n & 1) { multiSqMat(tmp, prod, XX); memcpy(prod, tmp, sizeof(sqmat_t)); } multiSqMat(tmp, XX, XX); memcpy(XX, tmp, sizeof(sqmat_t)); n >>= 1; } memcpy(Y, prod, sizeof(sqmat_t)); } int main(void) { int n; sqmat_t tmp; const sqmat_t Q = {{0, 1, 0}, {0, 0, 1}, {1, 1, 0}}; scanf("%d", &n); fastPowMat(tmp, Q, n); printf("%lld\n", (tmp[0][2] + tmp[1][2] + tmp[2][2]) % MOD); return 0; }