#include<stdio.h>

int main()

{

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

    int i,j;

    int sum =0;

    for(i=0;i<3;i++)

        {

             for(j=0;j<3;j++)

            {

                if(i==j || i+j==2);

                sum += arr[i][j];

            }   

        }

        printf("对角线元素之和是：%d\n",sum);

        return 0;

}