CF 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 from 0 to
p?-?1. He wants to insert n numbers, in the order they are given, into the hash table. For the
i-th number x_i, DZY will put it into the bucket numbered
h(x_i), where
h(x) is the hash function. In this problem we will assume, that
h(x)?=?x mod p. Operation
a mod b denotes taking a remainder after division
a 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 the
i-th insertion, you should output
i. If no conflict happens, just output
-1.

Input

The first line contains two integers,
p and n
(2?≤?p,?n?≤?300). Then n lines follow. The
i-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 5
0
21
53
41
53

Output

4

Input

5 5
0
1
2
3
4

Output

-1

//题意就是找相等的数，输出第二个的位置，但是要是最先发现的。
例如：10 5
      1 2 2 2 1
输出是3而不是5，因为先找到2和2相等，如果只用for循环，找到的是1和1相等输出是5.
第4个样例卡了很久，没看懂题目。。。。
#include <iostream>
using namespace std;
int main()
{   __int64 a[400];
    int n,t,i,j,p,k;
    while(scanf("%d%d",&p,&n)!=EOF)
    {   memset(a,0,sizeof(a));
        t=0;
        for(i=0;i<n;i++)
        {
            scanf("%I64d",&a[i]);
            a[i]=a[i]%p;
        }
        k=n;
        for(i=0;i<n-1;i++)
        {
            for(j=i+1;j<n;j++)
                if(a[i]==a[j])
                {
                    k=k<(j+1)?k:(j+1);
                        t=1;
                }

        }
        if(t==1)
            printf("%d\n",k);
       if(t==0)
           printf("-1\n");
    }
    return 0;
}

CF A. DZY Loves Hash