Submission #1693785

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Source Code Expand

// 解説を見た

#include <iostream>
#include <queue>
#include <vector>
#include <cmath>
#include <algorithm>
#include <map>
#include <iomanip>
#include <numeric>

using namespace std;
using ll = long long;
const ll INF = 1e9;
const ll MOD = 1e9 + 7;

int as[5];

int main() {
    int N;
    cin >> N;
    for (int i = 0; i < N; i++) {
        int a;
        cin >> a;
        as[a]++;
    }

    int ans = as[4];
    if (as[3] >= as[1]) {
        ans += as[1];
        ans += as[3] - as[1];
        as[1] = 0;
    } else {
        ans += as[3];
        as[1] -= as[3];
        as[3] = 0;
    }
    ans += ceil(as[2] / 2.0);
    if (as[2] % 2 == 1) {
        as[1] -= min(as[1], 2);
    }
    ans += ceil(as[1] / 4.0);

    cout << ans << endl;

    return 0;
}

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