#include<bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using mint=modint998244353; //1000000007;
using ll=long long;
using pp=pair<int,int>;
#define sr string 
#define vc vector
#define db double
#define fi first
#define se second
#define rep(i,n) for(int i=0;i<(int)n;i++)
#define pb push_back
#define all(v) v.begin(),v.end()
#define pque priority_queue
#define bpc(a) __builtin_popcount(a)
int main(){
   ll t,x,a,y,b;cin>>t>>a>>x>>b>>y;
   ll ans=0;
   if(t<0){
   	ans+=(-t+y-1)/y; t+=ans*y;
   	ans*=b;
   }
   ll res=1e18;
   for(ll i=0;i<x;i++){
   	ll nt=t+y*i; ll now=i*b;
   	now+=(nt/x)*a+nt%x;
   	res=min(res,now);
   }
   cout<<res+ans;
}