#include <bits/stdc++.h>
using namespace std;
#define nyahalo ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define otsumiko exit(0);
#define mikodanye priority_queue<pair<long long, long long>, vector<pair<long long, long long> >, greater<pair<long long, long long> > >
#define mikochi priority_queue<long long, vector<long long>, greater<long long> >
long long l, r, x, ao = 1, wd, ans, ca, cl, cr, cs, sl[500069], sx = 0;
vector<long long> wl[500069], ps[500069];
int main() {
nyahalo
long long i, j, ii;
cin >> l >> r;
for (i=1; i<=r; i++) {
cin >> x;
sx += x;
cs = 0;
ps[i].push_back(0);
for (j=1; j<=x; j++) {
cin >> wd;
cs += wd;
wl[i].push_back(wd);
ps[i].push_back(cs);
}
sl[i] = cs;
if (x != 1) {
ao = 0;
}
}
if (ao == 1) {
ans = 0;
for (i=1; i<=r; i++) {
wd = wl[i][0];
cr = wd;
cl = l-wd+1;
ca = max(0ll, cr-cl+1);
ans = max(ans, ca);
}
cout << ans << "\n";
otsumiko
}
if ((r == 2 && l<=1000000) || (l<=1000 && sx<=1000)) {
ans = 0;
for (i=1; i<=r; i++) {
ca = 0;
for (j=1; j<=l; j++) {
cl = *(lower_bound(ps[i].begin(), ps[i].end(), j)-1);
cr = sl[i]-cl;
cr = l+1-cr;
if (cr<=j) {
ca++;
}
}
ans = max(ans, ca);
}
cout << ans << "\n";
otsumiko
}
cout << "sek\n";
otsumiko
}
