题解

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

const int INF = 0x3f3f3f3f;

int main() {
    int L, S, T, M;
    cin >> L >> S >> T >> M;

    vector<long long> pos(M + 1);
    for (int i = 1; i <= M; ++i) {
        cin >> pos[i];
    }

    sort(pos.begin() + 1, pos.end()); 

    if (S == T) {
        long long ANS = 0;
        for (int i = 1; i <= M; i++) {
            if (pos[i] % S == 0)
                ANS++;
        }
        cout << ANS;
        return 0;
    }

    for (int i = 1; i <= M; i++) {
        long long delta = pos[i] - pos[i - 1];
        if (delta > 90) {
            pos[i] = pos[i - 1] + delta % 90;
        }
    }

    L = pos[M] + (L - pos[M]) % 90;

    vector<long long> a(L + 1, 0);
    for (int i = 1; i <= M; i++) {
        a[pos[i]] = 1;
    }

    vector<long long> f(L + 1, INF);
    f[0] = 0;

    for (int i = 1; i <= L; i++) {
        for (int j = S; j <= T; j++) {
            long long pos1 = i - j;
            if (pos1 < 0) break;
            f[i] = min(f[i], f[pos1] + a[i]);
        }
    }

    cout << f[L] << endl;

    return 0;
}