Addition of Diagonal Elements in Matrix

#include<stdio.h>
#include<conio.h>
void main()
{
int i,j,a[10][10],sum,m,n;
/* m - Number of rows 
   n - Number of Columns   */
printf("\nEnter the number of Rows : ");
scanf ("%d",&m);
printf("\nEnter the number of Columns : ");
scanf ("%d",&n);
/* Accept the Elements in m x n Matrix */
for(i=0;i<m;i++ )
       for(j=0;j<n;j++)
       {
       printf("Enter the Element a[%d][%d] : ", i , j);
       scanf("%d",&a[i][j]);
       } 
/* Addition of all Diagonal Elements */
sum = 0;
for(i=0;i<m;i++ )
       for(j=0;j<n;j++)
       {
        if ( i == j )
        sum = sum + a[i][j];
       } 
/*  Print out the Result */
printf("\nSum of All Diagonal Elements in Matrix : %d",sum); 
getch();
}

Output