#include <bits/stdc++.h> using namespace std; const int maxn = 10010; int n, a[maxn], cnt = 1, ans = 1; int main() { cin >> n; for (int i = 0; i < n; i ++) cin >> a[i]; for (int i = 1; i < n; i ++) { if (a[i] == a[i-1] + 1) { cnt ++; if (cnt > ans) ans = cnt; } else cnt = 1; } cout << ans << endl; return 0; }