Write a program that calculates the sum of elements of the first diagonal (right) in a square matrix.

#include <stdio.h>
#include <conio.h>
#define SIZE 50
void main()
{
	int A[SIZE][SIZE];    
 	int R;    	/* dimensions  */
 	int I, J;    	/* counters */
 	int sum;

	do {
		printf("Number of rows and columns of the square matrix  (max.%d) : ", SIZE);
		scanf("%d", &R);
	} while (R <= 0 || R > SIZE);



 	for (I=0; I<R; I++)
    		for (J=0; J<R; J++)
        	{
         		printf("A[%d][%d] : ",I,J);
         		scanf("%d", &A[I][J]);
        	}


 	printf("\nMatrix :\n");
 	for (I=0; I<R; I++)
    	{
     		for (J=0; J<R; J++)
          		printf("%7d", A[I][J]);
     		printf("\n");
    	}

 	sum=0;
 	for (I=0; I<R; I++)
    		for (J=0; J<R; J++)
        		if(I==J)
				sum+=A[I][J];

     	printf("The sum of the main diagonal is equal to %d.\n", sum);
	getch();
}