#include<stdio.h>
int main(void)
{
    int n;
    int student[50];
    int left;
    int right;
    int res=0;
    int middle=0;
    scanf("%d",&n);
    for(int i=0;i<n;i++)
        scanf("%d",&student[i]);
    scanf("%d %d",&left,&right);
    for(int i=0;i<n;i++)
    {
        if(student[i]<left)
            res+=left-student[i];
        else if(student[i]>right)
            res+=student[i]-right;
        else
            middle+=right-student[i];
    }
    if(middle>=res)
        printf("%d",res);
    else
        printf("-1");
    return 0;
}