#include<bits/stdc++.h>
#define REP(i,a,b) for(int i=a;i<=b;i++)

using namespace std;

const int maxn=1000100;
const int INF=(1<<29);

int n,t;

int main()
{
    while(cin>>n>>t){
        if(t==10){
            if(n==1){
                puts("-1");
                continue;
            }
            REP(i,1,n-1) printf("1");
            puts("0");
        }
        else{
            REP(i,1,n) printf("%d",t);
            puts("");
        }
    }
    return 0;
}

#include<bits/stdc++.h>
#define REP(i,a,b) for(int i=a;i<=b;i++)

using namespace std;

typedef long long ll;
const int maxn=1000100;
const int INF=(1<<29);
const ll p=1e9+7;

int n;
ll x3[maxn],x7[maxn];

int main()
{
    x3[0]=x7[0]=1;
    REP(i,1,maxn-1) x3[i]=(x3[i-1]*3)%p,x7[i]=(x7[i-1]*7)%p;
    while(cin>>n){
        printf("%I64d\n",(x3[n*3]+7*p-x7[n])%p);
    }
    return 0;
}

#include<bits/stdc++.h>
#define REP(i,a,b) for(int i=a;i<=b;i++)
#define MS0(a) memset(a,0,sizeof(a))

using namespace std;

typedef long long ll;
const int maxn=10001000;
const int INF=(1<<29);

ll n;
vector<int> prime;
bool isprime[maxn];

void getPrime()
{
    memset(isprime,1,sizeof(isprime));
    isprime[1]=0;
    REP(i,2,maxn-1){
        if(!isprime[i]) continue;
        for(int j=i+i;j<maxn;j+=i){
            isprime[j]=0;
        }
    }
    REP(i,1,maxn-1) if(isprime[i]) prime.push_back(i);
}

bool IsPrime(ll n)
{
    int cnt=0;
    ll t;
    for(int i=0;i<prime.size();i++){
        t=prime[i];
        if(t*t>=n) break;
        while(n%t==0) n/=t,cnt++;
    }
    while(n%t==0) n/=t,cnt++;
    if(n!=1) cnt++;
    return cnt==1;
}

int main()
{
    getPrime();
    while(cin>>n){
        ll p;
        for(p=n;;p--){
            if(IsPrime(p)) break;
        }
        ll a=p;
        n-=p;
        if(n==0){
            printf("1\n%I64d\n",a);continue;
        }
        if(IsPrime(n)){
            printf("2\n%I64d %I64d\n",a,n);continue;
        }
        ll b,c;
        for(b=2;b<n-1;b++){
            c=n-b;
            if(IsPrime(b)&&IsPrime(c)){
                break;
            }
        }
        printf("3\n%I64d %I64d %I64d\n",a,b,c);
    }
    return 0;
}