/*
ID: samikgo1
TASK:
LANG: C++
*/
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll,ll> pll;
#define all(x) x.begin(),x.end()
#define allr(x) x.rbegin(),x.rend()
#define f first
#define s second
//#define x first
//#define y second
const int INF = INT32_MAX;
const ll modulo = 1e4;
//#define int ll
int32_t main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
// freopen("input.in","r",stdin);
// freopen("haybales.out","w",stdout);
int W,n,v,w,k;
cin >> W >> n >> v >> w >> k;
assert(n==1);
cout << v*min(k,W/w);
}
