//C program to demonstrate the 
//Sum of diagonals of a matrix.
#include <stdio.h>

int main() 
{
    
    int i,j,m=3,n=3,a=0,sum=0;

    //input matrix
    int matrix[3][3]
        ={ {1,2,3}, {4,5,6}, {7,8,9} };

    //if both rows and columns are equal then it is
    //possible to calculate diagonal sum
    if(m=n){

        //printing the input matrix
        printf("The matrix is \n");

        //iterates number of rows
        for(i=0;i<m;i++){

            //iterates number of columns
            for(j=0;j<n;++j){
                printf(" %d",matrix[i][j]);
            }
            printf("\n");
        }
        for(i=0;i<m;++i){

            //calculating the main diagonal sum
            sum=sum+matrix[i][i];

            //calculating off diagonal sum
            a=a+matrix[i][m-i-1];
        }

        //printing the result
        printf("\nMain diagonal element sum is = %d\n",sum);
        printf("Off-diagonal elements sum is =%d\n",a);
    }
    else
        //if both rows and columns are not equal then it is
        //not possible to calculate the sum
        printf("not a sqaure matrix\n");
    return 0;
}