#include <stdio.h>
const int n_max = 1000;
long long c[n_max][n_max],
     	  p[n_max][n_max];
int i, j, n, d;
long long a, b;
int main()
{
	freopen("bile2.in","r", stdin);
	freopen("bile2.out", "w", stdout);
	scanf("%d %d", &n, &d);
	scanf("%lld %lld", &a, &b);
	c[0][0] = 1;	
	for (i = 1; i <= n; ++ i)
	{
		p[1][i] = 1;
		c[i][0] = 1;
		for (j = 1; j <= i; ++ j)
			c[i][j] = c[i-1][j-1] + c[i-1][j];
	}
	for (i = 2; i <= n; ++ i)
		for (j = i; j <=n; ++ j)
			p[i][j] = p[i][j-1] + p[i-1][j-d-1];
	for (i = 2; i <= n; ++ i)
	{
		int sum = 0;
		for (j = 1; j <= n; ++ j)
			sum += p[i][j];
/*		printf("i = %d sum = %d\n",i, sum);
		fflush(stdout);
*/		if (((c[n][i]-sum)/c[n][i]) > (a/b))
		{
			printf("%d\n",i);
			return 0;
		}
	}
	printf("%d\n", (n/(d+1))+1);
	return 0;
}