Sum of diagonal elements of a mxn matrix in C language

WAP that finds the sum of diagonal elements of a mxn matrix.

#include<stdio.h>

#include<conio.h>

void main()

{

 int mat[10][10],i,j,m,n,dg1=0,dg2=0;

 clrscr();

 printf("\n Input number of rows and columns of matrix\n");

 scanf("%d%d",&m,&n);

 if(m!=n)

 {

  printf("\n rows and columns are not same so diagonal sum cannot be calculated");

  getch();

  exit(0);

 }

 else

 {

  printf("\n Enter matrix elements :\n");

  for(i=0;i<m;i++)

  {

   for(j=0;j<n;j++)

   {

    scanf("%d",&mat[i][j]);

    if(i==j)

     dg1=dg1+mat[i][j];

    if(i+j==m-1)

     dg2=dg2+mat[i][j];

   }

  }

 printf("\n Matrix elements are \n");

 for(i=0;i<m;i++)

 {

   for(j=0;j<n;j++)

   {

      printf("%3d", mat[i][j]);

   }

   printf("\n");

 }

  printf("\n Sum of diagonal 1 :%d",dg1);

  printf("\n Sum of diagonl 2  :%d",dg2);

 }

 getch();

}

Output:-1

Input number of rows and columns of matrix

2

3

rows and columns are not same so diagonal sum cannot be calculated

Output:-2

Input number of rows and columns of matrix

3

3

 Enter matrix elements

1

2

3

4

5

6

7

8

9

Matrix elements are

1 2 3

4 5 6

7 8 9

Sum of diagonal 1 :15

Sum of diagonal 2 :15