//Normal

#define _GLIBCXX_DEBUG
#define ll long long
#include <bits/stdc++.h>
using namespace std;
using Graph = vector<vector<int>>;

void print(auto a){
  cout << a;
}

void prints(auto a){
  cout << a << " ";
}

void prints(){
  cout << " ";
}

void printl(auto a){
  cout << a << endl;
}

void printl(){
  cout << endl;
}

void fix(int n){
  cout << fixed << setprecision(n);
}

int main(){
  int A, B, C, D, E; cin >> A >> B >> C >> D >> E;
  
  vector<int> X(11000, 0);
  X[1] = D;
  for(int i = 2; i <= 10000; i++){
    int sum = X[i-1];
    
    if(i%10 == 0){
      if(E <= sum){
        sum -= E;
      }
    }
    
    X[i] = max(sum, 0);
  }
  
  int ans = 0;
  for(int i = 0; i <= A*(B-C); i++){
    ans += X[i];
  }
  
  printl(ans);
  
  return 0;
}