// Source: https://usaco.guide/general/io
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define eb emplace_back // faster than push_back xD
// pbds UwU
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
#define oset tree<ll, null_type,less<ll>, rb_tree_tag,tree_order_statistics_node_update> // use pair for ms
// my io library :D
#define m1(x) template<class T, class... U> void x(T&& a, U&&... b)
#define m2(x) (ll[]){(x forward<U>(b),0)...}
m1(pr){cout << forward<T>(a); m2(cout << " " <<); cout << "\n";}
m1(re){cin >> forward<T>(a); m2(cin >>);}
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
ll l, r, ans = 0; re(l, r);
vector<vector<ll>> x(r);
for (ll i{}; i < r; i++){
ll X; re(X);
for (ll j{}; j < X; j++){
ll c; re(c);
x[i].eb(c);
ans += c;
}
}
if (ans < l/2) pr(0);
else pr(ans);
}
