#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main(){
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
ll L, R;
if(!(cin >> L >> R)) return 0;
vector<pair<ll,ll>> alwaysCoveredIntervals; // đoạn bị che mãi mãi (inclusive)
for(int rr = 0; rr < R; ++rr){
ll n; cin >> n;
vector<ll> a(n);
for(int i = 0; i < n; ++i) cin >> a[i];
vector<ll> pref(n+1,0), suff(n+2,0);
for(int i = 1; i <= n; ++i) pref[i] = pref[i-1] + a[i-1];
for(int i = n; i >= 1; --i) suff[i] = suff[i+1] + a[i-1];
for(int i = 1; i <= n; ++i){
ll x = pref[i];
ll y = suff[i];
if(x + y >= L){
ll left = L - y;
ll right = x;
if(left < 1) left = 1;
if(right > L) right = L;
if(left <= right){
alwaysCoveredIntervals.emplace_back(left, right);
}
}
}
}
if(alwaysCoveredIntervals.empty()){
cout << 0 << '\n'; // không có vị trí bị che mãi mãi
return 0;
}
sort(alwaysCoveredIntervals.begin(), alwaysCoveredIntervals.end());
ll covered = 0;
ll curL = alwaysCoveredIntervals[0].first;
ll curR = alwaysCoveredIntervals[0].second;
for(size_t i = 1; i < alwaysCoveredIntervals.size(); ++i){
ll Ld = alwaysCoveredIntervals[i].first;
ll Rd = alwaysCoveredIntervals[i].second;
if(Ld > curR + 1){
covered += (curR - curL + 1);
curL = Ld; curR = Rd;
} else {
curR = max(curR, Rd);
}
}
covered += (curR - curL + 1);
if(covered > L) covered = L;
cout << covered << '\n';
return 0;
}
