import std.conv, std.stdio, std.string; import std.algorithm, std.array, std.bigint, std.container, std.math, std.range, std.regex, std.typecons; import core.bitop; class EOFException : Throwable { this() { super("EOF"); } } string[] tokens; string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; } int readInt() { return readToken().to!int; } long readLong() { return readToken().to!long; } real readReal() { return readToken().to!real; } void chmin(T)(ref T t, in T f) { if (t > f) t = f; } void chmax(T)(ref T t, in T f) { if (t < f) t = f; } int binarySearch(T)(in T[] as, in bool delegate(T) test) { int low = -1, upp = cast(int)(as.length); for (; low + 1 < upp; ) { int mid = (low + upp) >> 1; (test(as[mid]) ? low : upp) = mid; } return upp; } int lowerBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a < val)); } int upperBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a <= val)); } immutable MO = 10L^^9 + 7; int N; void main() { try { for (; ; ) { N = readInt(); auto dp = new long[][](N + 1, 3); dp[0][0] = 1; foreach (i; 0 .. N) { foreach (x; 0 .. 3) { // ken if (x < 2) { (dp[i + 1][x + 1] += dp[i][x]) %= MO; } // pa if (x > 0) { (dp[i + 1][0] += dp[i][x]) %= MO; } } } writeln(dp[N].sum % MO); } } catch (EOFException e) { } }