A. DZY Loves Hash

A. DZY Loves Hash

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

DZY has a hash table with p buckets, numbered from0 top - 1. He wants to insertn numbers, in the order they are given, into the hash table. For thei-th numberx_i, DZY will put it into the bucket numberedh(x_i), whereh(x) is the hash function. In this problem we will assume, thath(x) = x mod p. Operationa mod b denotes taking a remainder after divisiona by b.

However, each bucket can contain no more than one element. If DZY wants to insert an number into a bucket which is already filled, we say a "conflict" happens. Suppose the first conflict happens right after thei-th insertion, you should output i. If no conflict happens, just output-1.

Input

The first line contains two integers, p andn(2 ≤ p, n ≤ 300). Thenn lines follow. Thei-th of them contains an integer x_i(0 ≤ x_i ≤ 10⁹).

Output

Output a single integer — the answer to the problem.

Sample test(s)

Input

10 5021534153

Output

4

Input

5 501234

Output

-1

//水题不多说

//AC代码

#include<iostream>#include<queue>#include<algorithm>#include<cstdio>#include<cstring>#include<string>#include<map>using namespace std;int main(){    int p,n,x,y,j;    int z[301];    //while(1)    //{        cin>>p>>n;        map<int,int>Map;        memset(z,0,sizeof(z));        j=0;        for(int i=1;i<=n;i++)        {            cin>>x;            y=x%p;            Map[y]+=1;            if(Map[y]>1)            {                z[j++]=i;            }        }        if(j!=0)        {            cout<<z[0]<<endl;        }        else            cout<<-1<<endl;    //}    return 0;}