import numpy as np
import scipy as sp
import matplotlib.pyplot as plt


def main():
    N = 8                   # Number of points
    n = np.arange(0, N)     # Range of inputs

    x = (-1)**n             # Definition of signal
    X_N = sp.fft.fft(x)     # DFT of signal

    plt.stem(n, X_N)
    plt.show()


if __name__ == "__main__":
    main()