Глебу

#include <iostream>
#include <cmath>
#include <vector>
#include <queue>
#include <algorithm>
#include <string>
#include <stack>
#include <set>
#include <map>
#define pii pair <int,int>
#define vec vector
using namespace std;
using ll = long long;
using ld = long double;
using db = double;
void cv(vector <int> &v){
    for (auto x: v) cout<<x<<' ';
    cout<<"\n";
}

void cvl(vector <ll> &v){
    for (auto x: v) cout<<x<<' ';
    cout<<"\n";
}


void cvv(vector <vector <int> > &v){
    for (auto x: v) cv(x);
    cout<<"\n";
}

int n,why;

vector <int> S;



vector <int> ans;

vector <int> m;

void mnk(){
    n = S.size();
    m.resize(n,0);
    //cout<<"S\n";
    //cv(S);
    pii lr = {-1, -1};
    pii now;
    for (int i = 0; i < n;++i){
        int l = lr.first, r = lr.second;
        if (i >= l && i <= r){
            int idx = l +  (r - i);
            m[i] = min(r - i + 1, m[idx]);
        }
        while (i - m[i] >= 0 && i + m[i] < n && S[i - m[i]] == S[i + m[i]]){
            ++m[i];
        }
        now = {i - m[i] + 1, i + m[i] - 1};
        if (now.second > lr.second){
            lr = now;
        }
    }
    //cout<<"m\n";
    //cv(m);
    int k=-1;
    for (int i = 0; i < n; i+=2){
        if (i - m[i] == -1){
            k = (n - i) / 2;
            ans.push_back(k);
        }
    }
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin>>n>>why;
    S = {0};
    for (int i=0;i<n;++i) {
            int x;
            cin>>x;
            S.push_back(x);
            S.push_back(0);
    }
    mnk();
    sort(ans.begin(), ans.end());
    //cout<<"ans\n";
    cv(ans);
}
/*
6 2
1 1 2 2 1 1

*/