Need a little help

We got this problem yesterday. Our teacher said if we get it done before October he'll give us extra credit, but I don't really even know where to start. Just point me in the right direction por favor. Here's the problem:

Maze Surfing

You dirty rat. You're caught in a malicious lab experiment, and dropped into a maze. Your job is to find the cheese and thereby to prove your superior intelligence of the various rodent sopecies.

Program Input

The input file PROG13.IN describes a single maze. The first line of the file is an integer, N, indicating the number of rows and columns in the maze, constrained by: 8 < N < 19. The next N lines each contain N characters seperated by spaces. Walls are represented by '#', hallways by '.', the start position by 'M' and the cheese by 'C'.

Program Output
The program should write the maze to PROG13.OUT, drawing the shortest path from M to C with a series of '+' characters. You may assume that (1) there will be a valid path from M to C, and (2) there will only be one path from M to C (i.e., no loops). The path is not permitted to contain any diagnol movements.

Sample Input:

10 # # # # # # # # # # # . # M . . # . . # # . # # . # # # . # # . . . . . . . . # # # # # . # . # # # # . . . . # . # C # # # # # # # . # . # # . # . . . . # . # # . . . # . . . . # # # # # # # # # # #

Sample Output:

# # # # # # # # # # # . # M + . # . . # # . # # + # # # . # # . . . + + + . . # # # # # . # + # # # # . . . . # + # C # # # # # # # + # + # # . # . . . + # + # # . . . # . + + + # # # # # # # # # # #