#include <iostream>
using namespace std;
const int N = 1e5 + 10;
int q[N], s[N]; //q存数列,s存状态
int n;
int main()
{
cin >> n;
for (int i = 0; i < n; i ++ ) cin >> q[i];
int res = 0;
for (int i = 0, j = 0; i < n; i ++ ) //双指针i在右j在左
{
s[q[i]] ++ ; //更新每个值的状态
while (j < i && s[q[i]] > 1) s[q[j ++ ]] --; //发现重复值,j往右移动同时状态减1
res = max(res, i - j + 1); //更新最大子序列长度
}
cout << res << endl;
return 0;
}