【程序38】求一个3*3矩阵对角线元素之和

#include<stdio.h>
#define N 3
int main()
{
int i,j,a

,sum=0;
printf("Please input rectangle element(3*3)!\n");
for(i=0;i<N;i++)
for(j=0;j<N;j++)
scanf("%d",&a[i][j]);
for(i=0;i<N;i++)
sum+=a[i][i];
printf("The duijiaoxian he is %d\n",sum);
return 0;
}