Minimum moves to make array equal

Given an array and return the minimum number of operation (+,-) to make all values equal . In one move , you can subtract/add to the current value and its adjacent values . If no possible moves exist , return -1 ex:

1 0 5

1St move: 1   0<--5    => 1 1 4
2nd move: 1<--1<--4    => 2 1 3 
3rd move: 2   1<--3    => 2 2 2

 0 2 0
ans : -1 (not possible to make all equal)

I have tried to google and build approach , but could not