/*
    By: facug91
    From: http://coj.uci.cu/24h/problem.xhtml?abb=1240
    Name: Bingo!
    Number: 1240
    Date: 08/11/2013
*/

#include <iostream>
#include <cstdio>
#include <string>
#include <cstring>
#include <list>
#include <iterator>
#include <cstdlib>
#include <set>

using namespace std;

int main () {

    int n, b, aux, act;
    list<int> sobrantes;
    set<int> total;
    list<int>::iterator itr;

    cin>>n>>b;


    while ((n) && (b)) {
        for (;b--;) {
            cin>>aux;
            sobrantes.push_back(aux);
        }

        b = sobrantes.size();
        for (;b--;) {
            act = sobrantes.front();
            for (itr = sobrantes.begin(); itr != sobrantes.end(); itr++) {
                total.insert(abs(act - *itr));
            }
            sobrantes.pop_front();
        }

        if (total.size() == n+1) {
            printf("Y\n");
        } else {
            printf("N\n");
        }

        total.clear();

        cin>>n>>b;
    }




    return 0;
}