#include <iostream>
#include <vector>
#include <set>
#include <map>
#include <cstring>
#include <algorithm>
#include <stack>
#include <queue>
#include <fstream>
using namespace std;
typedef int ll;

int main(){
    ios_base::sync_with_stdio(false);
    int n, k;
    cin >> n >> k;

    vector<int> v(n);
    for(int i = 0; i < n; i++) {
        cin >> v[i];
    }

    vector<int> cnt(k, 0);
    int result = 0;
    multiset<int> ms;
    for(int i = 0; i < k; i++) {
        ms.insert(0);
    }

    int i = 0, j = 0;
    while(j < n) {
        if(*ms.begin() <= 3 and *ms.rbegin() <= 3) {
            if(v[j] < k) {
                ms.erase(ms.find(cnt[v[j]]));
                cnt[v[j]]++;
                ms.insert(cnt[v[j]]);
            }
            if(*ms.begin() == 3 and *ms.rbegin() == 3) {
                result = max(result, j - i + 1);
            }
            j++;
        }
        else {
            if(v[i] < k) {
                ms.erase(ms.find(cnt[v[i]]));
                cnt[v[i]]--;
                ms.insert(cnt[v[i]]);
            }
            if(*ms.begin() == 3 and *ms.rbegin() == 3) {
                result = max(result, j - i + 1);
            }
            i++;
        }
    }

    cout << result << endl;
    return 0;
}