#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <iostream>
#include <math.h>
using namespace std;
typedef long long LL;
LL gcd(LL a,LL b){
    return b==0?a:gcd(b,a%b);
}
LL lcm(LL a,LL b){
    return a/gcd(a,b)*b;
}
int main()
{
    int n;
    LL a;
    while(scanf("%d%lld",&n,&a)!=EOF,n&&a){
        LL ans = 1,num;
        for(int i=0;i<n;i++){
            scanf("%lld",&num);
            ans = lcm(ans,num);
        }
        printf("%lld\n",ans-a);
    }
    return 0;
}