whats wrong with my code: why its not accepted? for SUPW problem

import numpy as np

N=int(input())

l=list(map(int,input().split()))[:N]

arr=np.array(l)

b=0

x=N%3

y=N-x

j=0

if(N>2):

for i in range(0,y,3):

a=arr[i:i+3]

b=b+min(a)

if(i==y-3):

j=i+3

if(x==1 or x==2):

a = arr[j:j + x]

b = b + min(a)

print(b)