Codeforces 410C.Team[構造]

C. Team

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

Now it's time of Olympiads. Vanya and Egor decided to make his own team to take part in a programming Olympiad. They've been best friends ever since primary school and hopefully, that can somehow help them in teamwork.

For each team Olympiad, Vanya takes his play cards with numbers. He takes only the cards containing numbers 1 and 0. The boys are very superstitious. They think that they can do well at the Olympiad if they begin with laying all the cards in a row so that:

• there wouldn't be a pair of any side-adjacent cards with zeroes in a row; 
• there wouldn't be a group of three consecutive cards containing numbers one. 

Today Vanya brought n cards with zeroes and m cards with numbers one. The number of cards was so much that the friends do not know how to put all those cards in the described way. Help them find the required arrangement of the cards or else tell the guys that it is impossible to arrange cards in such a way.

Input

The first line contains two integers: n (1 ≤ n ≤ 106) — the number of cards containing number 0; m (1 ≤ m ≤ 106) — the number of cards containing number 1.

Output

In a single line print the required sequence of zeroes and ones without any spaces. If such sequence is impossible to obtain, print -1.

Examples

input

1 2

output

101

input

4 8

output

110110110101

input

4 10

output

11011011011011

input

1 5

output

-1

---

題意：構造一個序列0連續1個 1連續最多兩個

---

先考慮無解，然後需要110，然後10，最後1收尾

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
int n,m,l;
int main(int argc, const char * argv[]) {
    scanf("%d%d",&n,&m);
    if(n-1>m||2*n<m-2) {printf("-1");return 0;}
    
    if(m==n-1) printf("0"),l=m;
    else if(m==n) l=m;
    else{
        int t=m-n-2;
        for(int i=1;i<=t;i++) printf("110"),m-=2,n--;
        l=min(m,n);
    }
    for(int i=1;i<=l;i++) printf("10"),n--,m--;
    while(m) printf("1"),m--;
    return 0;
}