#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	long long t; cin >> t;
	long long x, a; cin >> x >> a;
	long long y, b; cin >> y >> b;
	long long ans = LINF;
	if (t >= 0) {
		rep(i, t / y + 1) {
			long long nt = t + i * b;
			long long sub = i * y;
			if (a >= x) {
				sub += (nt / a)*x + nt % a;
			}
			else {
				sub += nt;
			}
			chmin(ans, sub);
		}
	}
	else {
		int subt = -t;
		//long long l = ((subt + b - 1) / b)*y;
		long long r = ((subt + b - 1) / b)*y + subt % y;
		rep2(i, 0, r + 1) {
			long long nt = i * b + t;
			if (nt < 0)continue;
			long long sub = i * y;
			if (a >= x) {
				sub += (nt / a)*x + nt % a;
			}
			else {
				sub += nt;
			}
			chmin(ans, sub);
		}
	}
	cout << ans << endl;
	return 0;
}