#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%2==0 && j%2==0)
??????????????? sum+=arr[i][j];
??????? }
??? }
??? printf("對角線元素之和是：%d\n",sum);
??? return 0;???
}