#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef long double ld;
typedef vector<ll> vi;
typedef pair<ll, ll> pi;
#define FOR(i, j, k) for (ll i = j; i < (ll) k; ++i)
#define FORD(i, j, k) for (ll i = j; i >= (ll) k; --i)
#define nl "\n"
#define all(x) (x).begin(), (x).end()
#define sc second
#define fr first
#define pb push_back
void solve()
{
ll s, n;
cin >> s >> n;
ll v, w, k;
cin >> v >> w >> k;
if(w * k <= s) {
cout << v * k << nl;
} else {
cout << (s / w) * k << nl;
}
}
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
ll t = 1;
// cin >> t;
while (t--)
{
solve();
}
}
