#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"
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int A, B, C, D, E;
	cin >> A >> B >> C >> D >> E;
	int count = A * (B - C);
	long long ans = 0;
	rep(i, count) {
		if (0 == i) { ans += D; continue; }
		if (0 == (i + 1) % 10) {
			if (E <= D) {
				D = D - E;
			}
		}
		ans += D;
	}
	cout << ans << endl;
	return 0;
}