//

 #include <cstdio>

 #include <cstring>

 #include <cmath>

 #include <iostream>

 #define LL long long

 using namespace std ;

 LL gcd(LL x,LL y)

 {

     return y ==  ? x : gcd(y,x%y) ;

 }

 int main()

 {

     int I,a ;

     while(~scanf("%d %d",&I,&a))

     {

         if(I ==  && a == ) break ;

         int x ;

         LL ans = ;

         while(I--)

         {

             scanf("%d",&x) ;

             ans = (ans * x)/gcd(ans,x) ;

         }

         printf("%I64d\n",ans-a) ;

     }

     return  ;

 }