You have a special model for simulating fire. It is a rectangular grid containing cells of equal size. Each cell contains a digit indicating how many minutes it takes for that cell to burn completely once it catches fire. After a cell is completely burned, the fire spreads to its vertically and horizontally adjacent cells.
You are given a String field, where the j-th character of the i-th element is the digit of the cell at row i, column j. At minute 0, the cell at row 0, column 0 catches fire. Return the state of the field at the given minute. The return value must be a String formatted exactly like field, but with '*' characters representing cells that are on fire and '.' characters representing cells that have burned completely.