#include <iostream> using namespace std; int main() { int n; cin >> n; int matrix[10][10]; // 假设矩阵大小不超过10x10 int sum = 0; for (int i = 0; i < n; ++i) { for (int j = 0; j < n; ++j) { cin >> matrix[i][j]; if (i == j || i + j == n - 1) { sum += matrix[i][j]; } } } cout << sum << endl; return 0; }