#include <stdio.h>

int main(void) {

    int a, b, c, d, e;
	int x;
	int total = 0;
	int i;
    scanf("%d%d%d%d%d", &a, &b, &c, &d, &e);
	x = d;
	total = x;
	if(b == c){
		printf("0\n");
		return 0;
	}
	for(i = 2;i <= a * (b - c);i++){
		if(i % 10 != 0){
			total += x;
		}
		else {
			if(e <= x){
				x = x - e;
				if(x < 0)x = 0;
				total += x;
			}
			else {
				total += x;
			}
		}
	}
    printf("%d\n", total);

	return 0;
}