# P3131 [USACO16JAN]子共七Subsequences Summing to Sevens

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• 题目提供者 FarmerJohn2
• 评测方式 云端评测
• 标签 前缀和 USACO 2016
• 难度 普及-
• 时空限制 1000ms / 128MB
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## 题目描述

Farmer John's $N$ cows are standing in a row, as they have a tendency to do from time to time. Each cow is labeled with a distinct integer ID number so FJ can tell them apart. FJ would like to take a photo of a contiguous group of cows but, due to a traumatic childhood incident involving the numbers $1 \ldots 6$, he only wants to take a picture of a group of cows if their IDs add up to a multiple of 7.

给你n个数，分别是a[1],a[2],...,a[n]。求一个最长的区间[x,y]，使得区间中的数(a[x],a[x+1],a[x+2],...,a[y-1],a[y])的和能被7整除。输出区间长度。若没有符合要求的区间，输出0。

## 输入输出格式

输入格式：

The first line of input contains $N$ ($1 \leq N \leq 50,000$). The next $N$

lines each contain the $N$ integer IDs of the cows (all are in the range

$0 \ldots 1,000,000$).

输出格式：

Please output the number of cows in the largest consecutive group whose IDs sum

to a multiple of 7. If no such group exists, output 0.

## 输入输出样例

输入样例#1： 复制
7
3
5
1
6
2
14
10
输出样例#1： 复制
5

## 说明

In this example, 5+1+6+2+14 = 28.

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