def mod2(list1, list2):
    n = min(len(list1), len(list2))
    if n == 0:
        return 0.0
    
    avg1 = sum(list1[:n]) / n
    avg2 = sum(list2[:n]) / n
    
    numerator = 0
    denom1 = 0
    denom2 = 0
    
    for i in range(n):
        diff1 = list1[i] - avg1
        diff2 = list2[i] - avg2
        numerator += diff1 * diff2
        denom1 += diff1 * diff1
        denom2 += diff2 * diff2

    if denom1 == 0 or denom2 == 0:
        return 0.0

    correlation = numerator / ((denom1 * denom2) ** 0.5)

    return correlation