tricky one

[geekocoder]

Michael Scofield needs to break out of a prison, to save his brother from getting executed, on account of a crime he has not committed. To accomplish this, he conceals the layout of the prison in form of a tattoo, which is a rectangular grid of 1000*1000. This grid conceals 4 symbols with different values representing ease of various passages in the prison. He needs your help in determining the easiest path, represented by symbol with the highest value. The grid is filled with integers. You are given four symbols + , - , / , X. These mathematical symbols have the property that each line segment of these symbols is made of 3 integers. Value of the symbol is the sum of the digits with which it is formed. Find the largest possible value of the symbol formed in the grid.
Ex. 3 2 4 2 2 2 1 2 5 conceals a +, which has a value of 10. - which has a value 9, 6 and 8. X which has a value of 15. / which has a value of 7. The largest value of symbol here is 15.