c - How to add a border around a matrix? -

i have problem need process matrix toroid calculating sum of neighbours, have thought way: add border around matrix elements represent outline of matrix.to more specific, if had matrix:
1 2 3
4 5 6
7 8 9,
after adding border this:
9 7 8 9 7
3 1 2 3 1
6 4 5 6 4
9 7 8 9 7
3 1 2 3 1
bolded numbers represent initial matrix.note corners of border opposite corner of initial matrix(e.g. :the corner adjacent a₁₁(whose value 1) a₀₀,(whose value 9),the same a₃₃,the corner opposing a₁₁ in initial matrix ). far have come algorithm, pretty works fine, except rightmost column, or think.yes aware algorithm not have complexity, it's best come , have no memory/time restriction on problem.any suggestions error might be?(n number of lines, m number of columns

        (i=1; i<n+1; i++)         {             (j=1; j<m+1; j++)             {                 b[i][j]=a[i][j];             }         }         for(i=1; i<m+1; i++)         {             b[0][i]=b[n][i];             b[n+1][i]=b[1][i];         }         for(j=1; j<n+1; j++)         {             b[i][0]=b[i][m];             b[i][m+1]=b[i][1];         }         b[0][0]=b[n][m];         b[m+1][n+1]=b[1][1];         b[n+1][0]=b[1][m];         b[0][m+1]=b[n][1]; 

p.s.sorry if there grammar/spelling/ errors or ambiguos text, english far perfect if have questions ask them , try explain better.

your last loop iterator 'j' use 'i' index elements.