90分代码：
#include<bits/stdc++.h>
using namespace std;
#define int long long
struct node{
int a,b; double c,d,w;
}ar[25];
int n,m;double x,y;
bool cmp(node a,node b){
return a.w>b.w;
}
int sum;
signed main(){
cin>>n>>m>>x>>y;
double k=y/x;
for(int i=1;i<=m;i++){
cin>>ar[i].a>>ar[i].b>>ar[i].c>>ar[i].d;
ar[i].w=ar[i].d/ar[i].c;
}
sort(ar+1,ar+1+m,cmp);
for(int i=1;i<=m;i++){
if(ar[i].w<k||(ar[i].w<=k&&y>=ar[i].d&&x<=ar[i].c&&(n/x)>=(n/ar[i].c))){
int r4=n/x;
sum+=r4*y;
n-=r4*x;
}
int r1=ar[i].a/ar[i].b;
int r2=n/ar[i].c;
int r3=min(r1,r2);
sum+=ar[i].d*r3;
n-=r3*ar[i].c;
}
int r5=n/x;
while(r5>0){
sum+=r5*y;
n-=r5*x;
r5=n/x;
}
cout<<sum;
return 0;
}