#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<ll,ll> P;


int main(void){
	int i;

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

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

	ll mn=1e18;
	for(i=0;i<=1e7;i++){
		ll x=T+B*i;
		if(x<0) continue;
		ll j=x/A;
		ll r=x%A;
		mn=min(mn,r+X*j+Y*i);
	}

	cout << mn << endl;


	return 0;
}