#include <iostream>
using namespace std;
const int N = 100010;
int a[N], s[N];
int main() {
int n;
cin >> n;
int res;
for (int i = 0; i < n; i ++) scanf("%d", &a[i]);
//此时通过这种嵌套数组的方式来找到在每次循环中i, j最终停留的位置,从而来更新res;
for (int i = 0, j = 0; i < n; i ++) {
s[a[i]] ++;
while (j <= i && s[a[i]] > 1) {
s[a[j]] --;
j ++;
}
res = max(res, i - j + 1);
}
cout << res;
return 0;
}