#include <bits/stdc++.h>
using namespace std;
/*
run
g++ LASER.cpp -std=c++1y -o run.exe && ./run.exe
*/
// CONSTANTs
constexpr int MAX_N = 500000 + 5;
// GIVEN
int N, L;
vector<int> A[MAX_N];
// VARIABLEs
int x, y;
// FUNCTIONs
// SUBTASKs
bool checkSub2 = true;
namespace sub1 {
bool checkInput() {
return (checkSub2 && (N == 1));
}
int solve() {
cout << max(0ll, 1ll * A[1][0] + A[1][0] - L);
return 0;
}
}
namespace sub2 {
bool checkInput() {
return (checkSub2);
}
int solve() {
int maxX = A[1][0];
for (int i = 2; i <= N; ++i) maxX = max(maxX, A[i][0]);
cout << max(0ll, 1ll * maxX + maxX - L);
return 0;
}
}
namespace TRAU {
bool blocked[MAX_N << 1];
int solve() {
for (int i = 1; i <= N; ++i) {
long long sum = 0;
for (int j : A[i]) sum += j;
long long pre = A[i][0];
sum -= A[i][0];
if ((A[i][0] * 2) > (L - sum)) {
int lo = max(1ll, L - sum - A[i][0] + 1);
int hi = min(L, A[i][0]);
for (int j = lo; j <= hi; ++j) blocked[j] = true;
}
for (int j = 1; j < A[i].size(); ++j) {
sum -= A[i][j];
if ((A[i][j] * 2) > (L - sum - pre)) {
int lo = max(1ll, L - sum - A[i][j]);
int hi = min(1ll * L, A[i][j] + pre);
for (int k = lo; k <= hi; ++k) blocked[k] = true;
}
pre += A[i][j];
}
}
int res = 0;
for (int i = 1; i <= L; ++i) res += blocked[i];
cout << res;
return 0;
}
}
// MAIN
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr); cout.tie(nullptr);
// freopen("LASERS.INP", "r", stdin);
// freopen("LASERS.OUT", "w", stdout);
cin >> L >> N;
for (int i = 1; i <= N; ++i) {
cin >> x;
if (x > 1) {
checkSub2 = false;
}
while (x--) {
cin >> y;
A[i].push_back(y);
}
}
if (sub1::checkInput()) return sub1::solve();
if (sub2::checkInput()) return sub2::solve();
TRAU::solve();
}
