#include <stdio.h>

int main() {
    int arr[3][3] = {
        {1, 2, 3},
        {4, 5, 6},
        {7, 8, 9}
    };
    
    int n = 3;
    int answer = 0;
    
    for (int i = 0; i < n; i++) {
        answer += arr[i][i];
    }
    
    printf("%d\n", answer);
    return 0;
}