def fn(arr,d):
    s=0
    n=len(arr)
    for i in range(n):
        ts=0
        curr=0
        for j in range(i,n):
            if j==i:
                ts+=arr[j]
                curr+=arr[j]
            elif arr[j]-arr[j-1]==d:
                ts+=(arr[j]+curr)
                curr+=arr[j]
            else:
                break
        s+=ts
        
    return s

def main(arr):
    suma=0
    for x in arr:
        suma+=x
    
    return fn(arr,0)+fn(arr,1)-suma

print(main([5,8,8,10,11,12]))