use std::io;

fn main() {
	let mut s = String::new();
	io::stdin().read_line(&mut s).ok();
	let v:Vec<i32> = s.trim().split_whitespace().map(|e| e.parse().ok()
		.unwrap()).collect();
	
	let mut ans:i32 = 0;
	if (v[0] - v[1] >= v[0] - v[1] + v[2] * (v[3] - v[4])){
		ans = v[0] - v[1]
	} else {
		ans = v[0] - v[1] + v[2] * (v[3] - v[4])
	};
	
	println!("{}", ans);
}