/in/foo.cc: In function 'int main()':
/in/foo.cc:7:17: error: array size in new-expression must be constant
  a=new char[n][m];
                 ^
/in/foo.cc:7:17: error: the value of 'm' is not usable in a constant expression
/in/foo.cc:5:7: note: 'char m' is not const
  char m,n,*a;
       ^
/in/foo.cc:10:15: error: invalid types 'char[int]' for array subscript
    cin>>a[i][j];
               ^