#include<iostream>
#include<stdio.h>
using namespace std;

int main()
{
    setlocale(LC_ALL, "Russian");
    long n, m, sum = 0;
    cout << "Введите кол-во строк и столбцов";
    cin >> n >> m;
    long** arr = new long* [n+1];
    for (long i = 0; i <= n; i++)
        arr[i] = new long[m+1];
    cout << "Введите элементы матрицы: ";
    for (long i = 1; i <= n; i++)
        for (long j = 1; j <= m; j++){
            cin >> arr[i][j];
            if (i % 2 == 0){
                sum += arr[i][j];
            }
        }
    cout << "Сумма: " << sum << '\n';
    return 0;
}