def euler(n):
    s = 0
    for i in range(1,n+1):
        term = 1/i**2
        s = s + term
    x = (6*s)**0.5
    return(x)

def leibniz(n):
    s = 0
    for i in range(n):
        term = (-1)**i/(2*i+1)
        s = s + term
    x = 4*s
    return(x)

def wallis(n):
    p = 1
    for i in range(n):
        num = (2*i+2)**2
        den = (2*i+1)*(2*i+3)
        term = num/den
        p = p * term
    x = 2*p
    return(x)