#include<iostream>
#include<string>
#include<cmath>
using namespace std;
int n,sum=0,m=0;
const int N = 1e5 + 10;
int s[N] = { 0 };
int a[N];
int main()
{
cin >> n;
for (int i = 0; i < n; i++)
cin >> a[i];
for (int i=0, j = 0; i < n; i++)
{
if(!i)s[a[i]]++;
while (s[a[i]] < 2&&i<n)
i++,s[a[i]]++;
if (i - j > m)
m = i - j;
while (s[a[j]] < 2&&j<i)
s[a[j]]--, j++;
if (j == i)
break;
s[a[j]]--,j++,i--;
}
cout << m<<'\n';
return 0;
}