#line 1 "/opt/library/template.hpp"
#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using i64 = long long;
using u32 = unsigned int;
using u64 = unsigned long long;
using i128 = __int128;
using u128 = unsigned __int128;
using f128 = __float128;

template <class T>
constexpr T infty = 0;
template <>
constexpr int infty<int> = 1'000'001'000;
template <>
constexpr ll infty<ll> = ll(infty<int>) * infty<int> * 2;
template <>
constexpr u32 infty<u32> = infty<int>;
template <>
constexpr u64 infty<u64> = infty<ll>;
template <>
constexpr i128 infty<i128> = i128(infty<ll>) * infty<ll>;
template <>
constexpr double infty<double> = infty<ll>;
template <>
constexpr long double infty<long double> = infty<ll>;
#define inf infty<ll>

using pi = pair<ll, ll>;
using vi = vector<ll>;
using vvi = vector<vector<ll>>;
template <class T>
using vc = vector<T>;
template <class T>
using vvc = vector<vc<T>>;
template <class T>
using vvvc = vector<vvc<T>>;
template <class T>
using vvvvc = vector<vvvc<T>>;
template <class T>
using vvvvvc = vector<vvvvc<T>>;
template <class T>
using pq = priority_queue<T>;
template <class T>
using pqg = priority_queue<T, vector<T>, greater<T>>;

#define vv(type, name, h, ...) \
  vector<vector<type>> name(h, vector<type>(__VA_ARGS__))
#define vvv(type, name, h, w, ...)   \
  vector<vector<vector<type>>> name( \
      h, vector<vector<type>>(w, vector<type>(__VA_ARGS__)))
#define vvvv(type, name, a, b, c, ...)       \
  vector<vector<vector<vector<type>>>> name( \
      a, vector<vector<vector<type>>>(       \
             b, vector<vector<type>>(c, vector<type>(__VA_ARGS__))))

#define rep1(a) for (ll _ = 0; _ < (ll)(a); ++_)
#define rep2(i, a) for (ll i = 0; i < (ll)(a); ++i)
#define rep3(i, a, b) for (ll i = a; i < (ll)(b); ++i)
#define rep4(i, a, b, c) for (ll i = a; i < (ll)(b); i += (c))
#define rrep1(a) for (ll i = (a)-1; i >= (ll)(0); --i)
#define rrep2(i, a) for (ll i = (a)-1; i >= (ll)(0); --i)
#define rrep3(i, a, b) for (ll i = (b)-1; i >= (ll)(a); --i)
#define rrep4(i, a, b, c) for (ll i = (b)-1; i >= (ll)(a); i -= (c))
#define overload4(a, b, c, d, e, ...) e
#define rep(...) overload4(__VA_ARGS__, rep4, rep3, rep2, rep1)(__VA_ARGS__)
#define rrep(...) overload4(__VA_ARGS__, rrep4, rrep3, rrep2, rrep1)(__VA_ARGS__)

#define all(x) (x).begin(),(x).end()
#define len(x) (ll)(x.size())
#define elif else if
#define bit(x, i) (((x)>>(i))&1)

#define eb emplace_back
#define mp make_pair
#define mt make_tuple
#define fi first
#define se second

#define stoi stoll
#define abs llabs

#define MIN(v) *min_element(all(v))
#define MAX(v) *max_element(all(v))
#define LB(c, x) distance((c).begin(), lower_bound(all(c), (x)))
#define UB(c, x) distance((c).begin(), upper_bound(all(c), (x)))
#define UNIQUE(x) \
  sort(all(x)), x.erase(unique(all(x)), x.end()), x.shrink_to_fit()

ll popcnt(ll x) { return __builtin_popcountll(x); }
ll popcnt(u64 x) { return __builtin_popcountll(x); }
ll popcnt_mod_2(ll x) { return __builtin_parityll(x); }
ll popcnt_mod_2(u64 x) { return __builtin_parityll(x); }
ll topbit(ll x) { return (x == 0 ? -1 : 63 - __builtin_clzll(x)); }
ll topbit(u64 x) { return (x == 0 ? -1 : 63 - __builtin_clzll(x)); }
ll lowbit(ll x) { return (x == 0 ? -1 : __builtin_ctzll(x)); }
ll lowbit(u64 x) { return (x == 0 ? -1 : __builtin_ctzll(x)); }

template <typename T>
T floor(T a, T b) {
  return a / b - (a % b && (a ^ b) < 0);
}
template <typename T>
T ceil(T x, T y) {
  return floor(x + y - 1, y);
}
template <typename T>
T bmod(T x, T y) {
  return x - y * floor(x, y);
}
template <typename T>
pair<T, T> divmod(T x, T y) {
  T q = floor(x, y);
  return {q, x - q * y};
}

template<typename T> T SUM(const vector<T> &A) {
  T s = 0; for (auto &&a: A) s += a;
  return s;
}

template <typename T>
T POP(queue<T> &que) {
  T a = que.front();
  que.pop();
  return a;
}
template <typename T>
T POP(deque<T> &que) {
  T a = que.front();
  que.pop_front();
  return a;
}
template <typename T>
T POP(pq<T> &que) {
  T a = que.top();
  que.pop();
  return a;
}
template <typename T>
T POP(pqg<T> &que) {
  T a = que.top();
  que.pop();
  return a;
}
template <typename T>
T POP(vc<T> &que) {
  T a = que.back();
  que.pop_back();
  return a;
}

template <typename F>
ll binary_search(F check, ll ok, ll ng, bool check_ok = true) {
  if (check_ok) assert(check(ok));
  while (abs(ok - ng) > 1) {
    auto x = (ng + ok) / 2;
    (check(x) ? ok : ng) = x;
  }
  return ok;
}
template <typename F>
f128 binary_search_real(F check, f128 ok, f128 ng, ll iter = 100) {
  rep(iter) {
    f128 x = (ok + ng) / 2;
    (check(x) ? ok : ng) = x;
  }
  return (ok + ng) / 2;
}

// ? は -1
vc<int> s_to_vi(const string &S, char first_char) {
  vc<int> A(S.size());
  rep(i, S.size()) { A[i] = (S[i] != '?' ? S[i] - first_char : -1); }
  return A;
}

template <typename T, typename U>
vc<T> cumsum(vc<U> &A, ll off = 1) {
  ll N = A.size();
  vc<T> B(N + 1);
  rep(i, N) { B[i + 1] = B[i] + A[i]; }
  if (off == 0) B.erase(B.begin());
  return B;
}

// stable sort
template <typename T>
vi argsort(const vector<T> &A) {
  vi ids(len(A));
  iota(all(ids), 0);
  sort(all(ids),
       [&](ll i, ll j) { return (A[i] == A[j] ? i < j : A[i] < A[j]); });
  return ids;
}

// A[I[0]], A[I[1]], ...
template <typename T>
vc<T> rearrange(const vc<T> &A, const vi &I) {
  vc<T> B(len(I));
  rep(i, len(I)) B[i] = A[I[i]];
  return B;
}

template<typename T> inline bool chmax(T &a, T b) {return ((a<b)?(a=b,true):(false));}
template<typename T> inline bool chmin(T &a, T b) {return ((a>b)?(a=b,true):(false));}

inline void wt(const char c) { cout << c; }
inline void wt(const string s) { cout << s; }
inline void wt(const char *s) { cout << s; }

template <typename T>
void wt_integer(T x) {
  cout << (x);
}
template <typename T>
void wt_real(T x) {
  cout << fixed << setprecision(15) << (long double)(x);
}
template <typename T>
void wt_integer128(T x) {
  char buf[64];
  char *d = end(buf);
  d--; *d = '\0';
  __uint128_t tmp = ((x < 0)? -x : x);
  do {
    d--; *d = char(tmp%10 + '0'); tmp /= 10;
  } while (tmp);
  if (x < 0) {
    d--; *d = '-';
  }
  cout << d;
}

inline void wt(int x) { wt_integer(x); }
inline void wt(ll x) { wt_integer(x); }
inline void wt(i128 x) { wt_integer128(x); }
inline void wt(u32 x) { wt_integer(x); }
inline void wt(u64 x) { wt_integer(x); }
inline void wt(u128 x) { wt_integer128(x); }
inline void wt(double x) { wt_real(x); }
inline void wt(long double x) { wt_real(x); }
inline void wt(f128 x) { wt_real(x); }

template <class T, class U>
void wt(const pair<T, U> val) {
  wt(val.first); wt(' '); wt(val.second);
}
template <size_t N = 0, typename T>
void wt_tuple(const T t) {
  if constexpr (N < std::tuple_size<T>::value) {
    if constexpr (N > 0) { wt(' '); }
    const auto x = std::get<N>(t);
    wt(x);
    wt_tuple<N + 1>(t);
  }
}
template <class... T>
void wt(tuple<T...> tpl) {
  wt_tuple(tpl);
}
template <class T, size_t S>
void wt(const array<T, S> val) {
  auto n = val.size();
  for (size_t i = 0; i < n; i++) {
    if (i) wt(' ');
    wt(val[i]);
  }
}
template <class T>
void wt(const vector<T> val) {
  auto n = val.size();
  for (size_t i = 0; i < n; i++) {
    if (i) wt(' ');
    wt(val[i]);
  }
}

void print() { wt('\n'); }
template <class Head, class... Tail>
void print(Head &&head, Tail &&... tail) {
  wt(head);
  if (sizeof...(Tail)) wt(' ');
  print(forward<Tail>(tail)...);
}

void YES(bool t = 1) { print(t ? "YES" : "NO"); }
void NO(bool t = 1) { YES(!t); }
void Yes(bool t = 1) { print(t ? "Yes" : "No"); }
void No(bool t = 1) { Yes(!t); }
void yes(bool t = 1) { print(t ? "yes" : "no"); }
void no(bool t = 1) { yes(!t); }
void onez(bool t = 1) { print(t ? 1 : 0); }
#define endl '\n'
#define dump(x) {cerr << #x " = " << x << '\n';}
#line 2 "main.cpp"

int solve();
int main() {
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  while (!solve()) {break;}
  return 0;
}

int solve() {
  ll A, B, C, D, E;
  cin >> A >> B >> C >> D >> E;
  ll ans = -inf;
  rep(i, C+1) {
    chmax(ans, (A + D*i) - (B + E*i));
  }
  print(ans);
  return 0;
}