V1 = [0,2.08914,2.09140,2.61142,1.87594,2.01939,3.04507,2.43586,2.85422,2.40610,2.2348,2.10261,3.06490,3.02176,3.15124,3.52609,4.01823,4.48565,3.41086,3.23834,3.82458]
d = [0,0.25,0.25,0.25,0.25,0.25,0.25,0.25,0.25,0.25,0.25,0.25,0.4,0.4,0.4,0.4,0.6,0.6,0.6,0.6,0.6]
a = []
total = 0
calc = 0

for i in range(0,len(V1)):
    for j in range(i+1,len(V1)):
        if (d[i] != d[j] and d[i] != 0):
            calc += 1
            temp = (V1[j]**2 - V1[i]**2) / (2*(d[j]-d[i]))
            total += temp
            a.append(temp)

print(total/calc)