class Matrix:
    Q = [[0, 1],
         [1, 1]]

    def __init__(self):
        self.__memo = {} #add memorization

    def __multiply_matrices(self, M1, M2):# multiply two 2x2 matrices line by column
        a11 = M1[0][0]*M2[0][0] + M1[0][1]*M2[1][0]
        a12 = M1[0][0]*M2[0][1] + M1[0][1]*M2[1][1]
        a21 = M1[1][0]*M2[0][0] + M1[1][1]*M2[1][0]
        a22 = M1[1][0]*M2[0][1] + M1[1][1]*M2[1][1]
        r = [[a11, a12], [a21, a22]]
        return r

    def __get_matrix_power(self, M, p):
        if p == 1:# if p was 1 we return matrix itself
            return M
        if p in self.__memo:# if we've already counted this power we return reminded matrix
            return self.__memo[p]
        K = self.__get_matrix_power(M, int(p/2)) # recursively power matrix to p/2 power
        R = self.__multiply_matrices(K, K) #matrix to matrix power = 2
        self.__memo[p] = R# remind it
        return R

    def get_num(self, n):
        if n == 0:#start num
            return 0;
        if n == 1:#start num
            return 2;
        powers = []
        p = 0
        for digit in reversed(bin(n-1)[2:]):# get bit representation of number
            if digit == '1':
                powers.append(int(pow(2, p)))# if bit = 1 then there was 1*2^p in number -> remind 2^p
            p += 1
        matrices = [self.__get_matrix_power(Matrix.Q, p)
                    for p in powers] #save all intermediate result
        while len(matrices) > 1:
            M1 = matrices.pop()
            M2 = matrices.pop()
            R = self.__multiply_matrices(M1, M2)#multiply them
            matrices.append(R)

        k = matrices[0][0][0] + matrices[0][1][0]# last matrix will contain all needed results
        mm = matrices[0][0][1] + matrices[0][1][1]
        return k + mm

mat = Matrix()
tt = int(input())
num = mat.get_num(tt)
print(num)