A.Sredina

#include <iostream>

using namespace std;


int main()
{
    int n, m;
    cin >> n >> m;

    float a[n][m];

    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            cin >> a[i][j];
        }
    }

    float sredina = 0;
    for (int i = 0; i < m; i++) {
        sredina += a[1][i];
    }

    sredina /= m;
    cout << sredina << endl;

    return 0;
}