#include<stdio.h>
int main(void){
	int a,b,c,d,e;
	scanf("%d%d%d%d%d",&a,&b,&c,&d,&e);
	int count = (b - c) * a;
	long long ans = 0;
	int x;
	
	x = d;
	//printf("%d ",count);
	for(int i=1;i<=count;i++){
		if(i == 1){
			ans = d;
			continue;
		}
		if(i%10 == 0){
			if(e <= x){
				ans += x - e;
				x = x - e;
			}
		}
		ans += x;
		//printf("%d ",x);
	}
	printf("%lld\n",ans);
	return 0;
}