#include<stdio.h>
FILE *fin,*fout;
long num[51],n,i,xia,shang;
int main()
{
	fin=fopen("groupa.in","rb");
	fout=fopen("groupa.out","wb");
	fscanf(fin,"%ld\n",&n);
	for(i=1;i<=n;i++)
		fscanf(fin,"%ld",&num[i]);
	fscanf(fin,"\n");
	fscanf(fin,"%ld%ld",&xia,&shang);
	long budao=0,chaole=0,jushang=0,juxia=0;
	for(i=1;i<=n;i++)
	{
		if(num[i]<xia)budao=budao+xia-num[i];
		if(num[i]>shang)chaole=chaole+num[i]-shang;
		if(num[i]<=shang&&num[i]>=xia){jushang=jushang+shang-num[i];juxia=juxia+num[i]-xia;}
	}
	if(chaole==budao)fprintf(fout,"%ld",budao);
	if(chaole<budao)
	{
		if(chaole+juxia+shang-xia<budao)fprintf(fout,"-1");
		else fprintf(fout,"%ld",budao);
	}
	if(chaole>budao)
	{
		if(jushang+budao+shang-xia<chaole)fprintf(fout,"-1");
		else fprintf(fout,"%ld",chaole);
	}
	fclose(fin);
	fclose(fout);
	return 0;
}