D1.cpp

// #pragma GCC optimize("Ofast,unroll-loops")
// #pragma GCC target("avx,avx2,fma")

#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define ull unsigned long long
#define dd double
#define ld long double
#define sl(n) scanf("%lld", &n)
#define si(n) scanf("%d", &n)
#define sd(n) scanf("%lf", &n)
#define pll pair <ll, ll>
#define pii pair <int, int>
#define mp make_pair
#define pb push_back
#define all(v) v.begin(), v.end()
#define inf (1LL << 61)
#define loop(i, start, stop, inc) for(ll i = start; i <= stop; i += inc)
#define for1(i, stop) for(ll i = 1; i <= stop; ++i)
#define for0(i, stop) for(ll i = 0; i < stop; ++i)
#define rep1(i, start) for(ll i = start; i >= 1; --i)
#define rep0(i, start) for(ll i = (start-1); i >= 0; --i)
#define ms(n, i) memset(n, i, sizeof(n))
#define casep(n) printf("Case %lld:", ++n)
#define pn printf("\n")
#define pf printf
#define EL '\n'
#define fastio std::ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);

const ll sz = 2e5 + 10;
ll ara[sz], cnt[105], prv[2*sz], n;

inline ll solve(ll v1, ll v2)
{
    ms(prv, -1);

    ll sum = 0, ret = 0;
    prv[0+sz] = 0;

    for1(i, n) {

        if(ara[i] == v1)
            sum++;
        else if(ara[i] == v2)
            sum--;

        if(prv[sum+sz] != -1)
            ret = max(ret, i - prv[sum+sz]);
        else
            prv[sum+sz] = i;
    }

    return ret;
}

int main()
{
    ll f = 0, num = 0;
    cin >> n;

    for1(i, n) {
        sl(ara[i]);

        cnt[ ara[i] ]++;

        if(cnt[ ara[i] ] > f) {
            f = cnt[ ara[i] ];
            num = ara[i];
        }
    }

    ll ans = 0;
    for1(i, 100) {
        if(i != num)
            ans = max(ans, solve(num, i));
    }

    cout << ans << EL;

    return 0;
}