import matplotlib.pyplot as plt
def Euler(x_f,n) :
    x=1
    y=0
    h=x_f/n
    abscisse=[1]
    ordonnee=[0]
    for i in range(n) :
        y=y+h/x
        x=x+h
        abscisse.append(x)
        ordonnee.append(y)
    plt.plot(abscisse,ordonnee,"r")
    plt.show()