#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
using intt = int64_t;
intt sum(const long &a, const long &b) { return (a + b) * (b - a + 1) / 2; }
vector<char> alphabet={'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
int main() {
cout << fixed << setprecision(10);
  int a,b,c,d,e;
  cin>>a>>b>>c>>d>>e;
  b-=c;
  int x=a*b;
  int p=0;
  int q=d;
  for(int i=1;i<=x;i++){
      if(i%10!=0){
          p+=q;
      }
      else if(e<=q){
          q=max(0,q-e);
          p+=q;
      }
      else{
          p+=q;
      }
      
  }
  cout<<p<<endl;
}