//-------------------------------------------AC code-------------------------------------------//

#include<algorithm>
#include<iostream>
#include<cstdio>

using namespace std;

typedef long long LL;

const int N = 20;
int n;
LL ans = -0x7fffffff;

struct WEEK{
    int a, b, c, d;
}w[N];

void dfs(int week, LL OI, LL WHK){
    if(week == n){
        if(OI * WHK > ans)
            ans = OI * WHK;
        return;
    }
    dfs(week+1, OI + w[week+1].c, max(1ll*0, WHK - w[week+1].d));
    dfs(week+1, max(1ll*0, OI - w[week+1].b), WHK + w[week+1].a);
}

int main(){
    freopen("week.in", "r", stdin);
    freopen("week.out", "w", stdout);
    scanf("%d", &n);
    for(int i = 1; i <= n; i++)
        scanf("%d%d%d%d", &w[i].a, &w[i].b, &w[i].c, &w[i].d);
    dfs(0, 1ll*0, 1ll*0);
    cout << ans;
    return 0;
}