#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0;i<int(n);i++)
typedef long long ll;
typedef pair<int,int> P;


int main(void){
	ll i,j;

	cin.tie(0);  ios_base::sync_with_stdio(false);

	ll T;
	cin >> T;
	ll X,A,Y,B;
	cin >> X >> A >> Y >> B;

	ll mn=1e18;
	for(i=0;i<=10000;i++){
		for(j=0;j<=10000;j++){
			if(A*i-B*j>T) continue;
			ll d=(X-A)*i+(Y+B)*j+T;
			if(d<0) continue;
			mn=min(mn,d);
		}
	}

	cout << mn << endl;

	return 0;
}