#include <bits/stdc++.h> using namespace std; using ll = long long; using P = pair<ll,ll>; #define fix(x) fixed << setprecision(x) #define asc(x) x, vector<x>, greater<x> #define rep(i, n) for(ll i = 0; i < n; i++) #define all(x) (x).begin(),(x).end() template<class T>bool chmin(T&a, const T&b){if(a>b){a=b;return 1;}return 0;} template<class T>bool chmax(T&a, const T&b){if(a<b){a=b;return 1;}return 0;} int main(){ cin.tie(nullptr); ios::sync_with_stdio(false); ll t,x,a,y,b,ans = (1LL<<60); cin >> t >> x >> a >> y >> b; rep(i,1e7+1){ if(t+b*i<0) continue; chmin(ans, i*y+(t+b*i)/a*x+(t+b*i)%a); } cout << ans << '\n'; return 0; }