#include <iostream> #include <iomanip> using namespace std; int main() { cout << "输入三行三排九个数" << endl; int a[9], i,sum=0; for (i = 0;i < 9;i++) { cin >> a[i]; } for (i = 0;i < 9;i=i + 2) { sum += a[i]; } cout << "这个矩形框对角线的和为:" << sum << endl; }