void readEdge (int *i, int *j);
/* Scans input to read a blocked edge.
   Returns the indices i and j in m[13][13] of an edge.
   Call this function with pointers to the variables 
   that should receive the values, e.g.
       readEdge (&x, &y);
*/

void readStation (int *i, int *j);
/* Scans input to read a station.
   Returns the indices i and j in m[13][13] of a station.
 */

void printCrossingName (int i, int j);
/* Print the name of the crossing with indices i and j in m[13][13]/ */

void printMatrix (int m[][13]);
/* Print the elements of the matrix m[13][13]. */