#include <stdio.h>
#include <stdbool.h>

int MMC_2(int n1, int n2) {

    int resto, x = n1, y = n2;

    do {
        resto = x % y;

        x = y;
        y = resto;

    } while (resto != 0);

    return ( n1 * n2) / x;
}

int MMC_Geral(int *TQ, int N){
    int mmc = TQ[0];

    if (N!=1){
        int i = 0;
        for (i = 1; i < N; i++){
            mmc = MMC_2(mmc, TQ[i]);
        }
    }

    return mmc;

}

int acharX(int mmc, int T, int N, int *TQ){
    int i = 0, x = 0;

    for (i = 2; i <= T; i++){
            int Y = MMC_2(mmc, i);
            bool isInvalido = false;
            if (Y == T){
                int j = 0;
                for (j = 0; j < N; j++){
                    if (i==TQ[j]){
                        isInvalido = true;
                        break;
                    }
                }
                if (!isInvalido){
                    x = i;
                    break;
                }
            }
    }

    return x;

}

int main(void){
    int N = 0, T = 0; //número de bolas e tempo das N+1 bolas
    scanf("%d %d", &N, &T);

    while((N!=0) && (T!=0)){
        int *TQ = (int*) malloc(N*sizeof(int)); //tempo de quique de cada uma das bolas

        int i = 0;
        for (i = 0; i < N; i++){
            scanf("%d", &TQ[i]);
        }

        int mmc = MMC_Geral(TQ, N);
        int x = acharX(mmc, T, N, TQ);

        if (x==0){
            printf("Impossivel\n");
        }
        else{
            printf("%d\n", x);
        }

        scanf("%d %d", &N, &T);
    }

    return 0;

}