#include <bits/stdc++.h>
using namespace std;
#define rep(i,l,r) for(int i=(l);i<(r);++i)
typedef long long ll;

int main(){
	int a,b,c,d,e; cin>>a>>b>>c>>d>>e;
	if(b-c==0) cout<<0<<endl;
	else if(d<e) cout<<(b-c)*a*d<<endl;
	else {
		int r=(b-c)*a;
		int x=d, ans=d;
		rep(i,2,r+1){
			if(i%10==0&&e<=x) x-=e;
			ans+=x;
		}
		cout<<ans<<endl;
	}
}