// Knapsack DP is harder than FFT.
#include<bits/stdc++.h>
using namespace std;
typedef int64_t ll; typedef pair<int,int> pii; typedef pair<ll,ll> pll;
#define ff first
#define ss second
#define pb emplace_back
#define FOR(i,n) for(int i=0;i<(n);++i)
#define FOO(i,a,b) for(int i=(a);i<=int(b);++i)
#define OOF(i,a,b) for(int i=(a);i>=int(b);--i)
#define AI(x) begin(x),end(x)
template<class I>bool chmax(I&a,I b){return a<b?(a=b,true):false;}
template<class I>bool chmin(I&a,I b){return b<a?(a=b,true):false;}
inline ll cdiv(ll x,ll m){return x/m+(x%m?(x<0)^(m>0):0);}
#ifdef OWO
#define safe cerr<<"\033[1;32m"<<__PRETTY_FUNCTION__<<" - "<<__LINE__<<" JIZZ\033[0m\n"
#define debug(args...) SDF(#args, args)
#define OIU(args...) ostream& operator<<(ostream&O,args)
#define LKJ(S,B,E,F) template<class...T>OIU(S<T...>s){O<<B;int c=0;for(auto i:s)O<<(c++?", ":"")<<F;return O<<E;}
LKJ(vector,'[',']',i)LKJ(deque,'[',']',i)LKJ(set,'{','}',i)LKJ(multiset,'{','}',i)LKJ(unordered_set,'{','}',i)LKJ(map,'{','}',i.ff<<':'<<i.ss)LKJ(unordered_map,'{','}',i.ff<<':'<<i.ss)
template<class T,size_t N>OIU(array<T,N>a){return O<<vector<T>(AI(a));}template<class...T>OIU(pair<T...>p){return O<<'('<<p.ff<<','<<p.ss<<')';}template<class...T>OIU(tuple<T...>t){return O<<'(',apply([&O](T...s){int c=0;(...,(O<<(c++?", ":"")<<s));},t),O<<')';}
template<class...T>void SDF(const char* s,T...a){int c=sizeof...(T);if(!c){cerr<<"\033[1;32mvoid\033[0m\n";return;}(cerr<<"\033[1;32m("<<s<<") = (",...,(cerr<<a<<(--c?", ":")\033[0m\n")));}
#else
#pragma GCC optimize("Ofast")
#define safe ((void)0)
#define debug(...) ((void)0)
#endif
const ll inf = 1e9, INF = 4e18;

vector<int> f, d, t;

ll check(int p, int lim){
    ll tot = 0;
    for(int i = 1; i <= p; ++i){
        if(d[i] == 0){
            if(f[i] >= lim) return INF;
            continue;
        }
        tot += cdiv(f[i] - lim + 1, d[i]);
    }
    return tot;
}

ll calc(int T, int p){
    int l = 0, r = 1e5 + 1, m;
    ll ret;
    while(l < r){
        // choose every value >= l
        m = (l + r) / 2;
        ret = check(p, m);
        if(ret > T) l = m + 1;
        else r = m;
    }

    ll ans = 0;
    for(int i = 1; i <= p; ++i){
        if(f[i] < l) continue;
        ll x = cdiv(f[i] - l + 1, d[i]);
        ans += (f[i] + (f[i] - d[i] * (x-1))) * x / 2;
        T -= x;
    }

    if(l - 1 > 0) ans += (l-1) * T;

    return ans;
}

void solve(int T, int n){
    f.assign(n + 1, 0);
    d.assign(n + 1, 0);
    t.assign(n + 1, 0);
    for(int i = 1; i <= n; ++i) cin >> f[i];
    for(int i = 1; i <= n; ++i) cin >> d[i];
    for(int i = 1; i <= n; ++i) cin >> t[i];

    ll ans = 0;
    for(int i = 1; i <= n; ++i){
        T -= t[i];
        if(T <= 0) break;
        chmax(ans, calc(T, i));
    }
    cout << ans << '\n';
}

int32_t main(){
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    int T, n;
    while(cin >> T >> n) solve(T, n);
    return 0;
}