#include <stdio.h>

int main(){
	// 野菜の数・肉の数・比率・許容量
	int vegetables, meat, proportion, all;
	scanf("%d%d%d%d",&vegetables,&meat,&proportion,&all);
	// 野菜を食べた個数
	int count = 0;
	int i = 0;
	while( i != all){
		if(meat > proportion){
			i += proportion;
			meat -= proportion;
		}
		if(vegetables != 0){
			vegetables -= 1;
			i++;
			count++;
		}
		if(meat == 0 || vegetables == 0){
			printf("%d",count);
			return 0;
		}
	}
	printf("%d",count);
}