Area Under the hill

areaUnderhill.py

def solve(self, A):
            A.append(0)
            n = len(A)
            res = 0 
            
            x =  1 
            for i in range(1,n):
                res += x*A[i]
                x+=1
            x = 1
            for i in A:
                res -= i *  x 
                x +=1

            res = abs(res)

            return res