#include<bits/stdc++.h>
#define M 20004
using namespace std;
 
int n, a[M], u[M], dp[M];
 
int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);     cout.tie(0);
 
    u[1] = 1;
    for(int i = 2; i <= 20000; i++)
        u[i] = u[i - 1] + i;
    cin >> n;
    int ans = 0;
    int d = 0;
    for(int i = 1; i <= n; i++)
    {
        cin >> a[i];
        if(binary_search(u + 1, u + 20001, a[i]) && (d == 0 || a[i] >= a[i - 1]))
            d++;
        else
        {
            ans = max(ans, d);
            d = 0;
        }
    }
    ans = max(ans, d);
    cout << ans;
}
 

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OAoyCjIwMDcKNgo2CjE1CjE2CjMKMjEK

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