#include<iostream>
#include<string>
#include<algorithm>    
#include<cmath>
#include<ctime>
#include<map>
#include<vector>
#include<math.h>
#include<stdio.h>
#include<stack>
#include<queue>
#include<tuple>
#include<cassert>
#include<set>
#include<bitset>
#include<functional>
#include <fstream>
//#include<bits/stdc++.h>
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#define rep(i, x) for(ll i = 0; i < x; i++)
#define rep2(i, x) for(ll i = 1; i <= x; i++)
#define all(a) (a).begin(),(a).end()
#define puts(x) cout << (x) << "\n"
using ll = long long;
using ld = long double;
using namespace std;
const ll INF = 1000000000000000000;
const int intINF = 1000000000;
const ll mod = 1000000007;
const ll MOD = 998244353;
const ld pi = 3.141592653589793238;
//const ld EPS = 1e-9;

bool isprime(int p) {
	if (p == 1) return false;
	for (int i = 2; i < p; i++) {
		if (p % i == 0) return false;
	}
	return true;
}
ll gcd(ll a, ll b) {
	if (a < b)swap(a, b);
	if (a % b == 0)return b;
	return gcd(b, a % b);
}
// 返り値: a と b の最大公約数
// ax + by = gcd(a, b) を満たす (x, y) が格納される
//main関数内に extGCD(a, b, x, y); でx, yに解が格納
ll extGCD(ll a, ll b, ll& x, ll& y) {
	if (b == 0) {
		x = 1;
		y = 0;
		return a;
	}
	ll d = extGCD(b, a % b, y, x);
	y -= a / b * x;
	return d;
}
ll lcm(ll a, ll b) {
	return a / gcd(a, b) * b;
}
ll keta(ll n) {
	ll res = 0;
	while (n >= 1) {
		res += n % 10; n /= 10;
	}
	return res;
}
ll modpow(ll x, ll y) {
	ll res = 1;
	while (y) {
		if (y % 2) { res *= x; res %= mod; }
		x = x * x % mod; y /= 2;
	}
	return res;
}
ll nCk(ll n, ll k) {
	ll a = 1, b = 1;
	for (int h = n - k + 1; h <= n; h++) { a *= h; a %= mod; }
	for (int h = 1; h <= k; h++) { b *= h; b %= mod; }
	return a * modpow(b, mod - 2) % mod;
}
//printf("%.10f\n", n);
typedef pair <ll, ll> P;
typedef pair <ld, ll> pp;
ll dx[4] = { 1, 0, -1, 0 }, dy[4] = { 0, 1, 0, -1 };
struct edge { ll to, cost; };
struct status {
	ll ima;
	ll cost;

	bool operator<(const status& rhs) const { return cost < rhs.cost; };
	bool operator>(const status& rhs) const { return cost > rhs.cost; };
};



signed main() {
	ios::sync_with_stdio(false);
	std::cin.tie(nullptr);
	//cout << fixed << setprecision(15);

	//input
	ll a, b, c, d, e; cin >> a >> b >> c >> d >> e;
	ll ko = a * (b - c);
	ll ans = 0, mae = 0;
	rep2(i, ko) {
		if (i == 1) { ans += d; mae = d; }
		else {
			if (i % 10 == 0 && mae >= e) { mae -= e; }
			ans += mae;
		}
	}
	cout << ans << endl;
	return 0;
}