原题

//代码
#include <bits/stdc++.h>
using namespace std;
int a[10005];
int main()
{
	int n,maxn = -1,cnt = 1;
	cin >> n;
	for (int i = 1;i <= n;i++) cin >> a[i];
	for (int i = 1;i <= n - 1;i++)
	{
		if (a[i] + 1 == a[i + 1]) cnt++;
		else if (cnt > maxn) maxn = cnt,cnt = 0;
		else cnt = 1;
	}
	if (cnt > maxn) maxn = cnt;
	cout << maxn;
}