Traceback (most recent call last):
  File "C:/Users/Αλέξανδρος/Desktop/1.py", line 12, in <module>
    k=k+C[s]
IndexError: list index out of range

a=0
b=0
s=0
k=0
A = [0 for a in range(1000)]
B = [0 for b in range(1000)]
C = [0 for s in range(1000000)]
while a<=1000:
    C[s]=(A[a]**2+B[b]**2)**0.5
    a=a+1
    s=s+1
    k=k+C[s]
    if a==1000:
        b=b+1
        a=0
if a==1000 and b==1000:
    print (k/1000000)