建议改小时限 / 改大数据。

#include <bits/stdc++.h>
using namespace std;
//#define int long long
typedef long long ll;
typedef pair<int, int> pr;
#define up(i, l, r) for(int i = (l); i <= (r); i++)
#define down(i, r, l) for(int i = (r); i >= (l); i--)
const int mod = 1000000007;
const int base = 2333;
const double eps = 1e-6;

inline int read() {
	int x = 0, f = 1; char ch = getchar();
	while(ch < '0' || ch > '9') { if(ch == '-') f = -1; ch = getchar(); }
	while(ch >= '0' && ch <= '9') { x = (x << 1) + (x << 3) + (ch ^ 48); ch = getchar(); }
	return x * f;
}

int t, n, m, k, Q, T, _, ans = 0, cnt = 0;
int a[1000007];
bool flag = 0;

signed main() {
	n = read();
	cnt = n / 3 + n / 5 - n / 15;
	while(1) {
		t = n + cnt;
		cnt = 0;
		for(int i = n + 1; i <= t; i++)
			if(i % 3 == 0 || i % 5 == 0) cnt++;
		if(cnt == 0) {
			cout << t;
			return 0;
		}
		n = t;
	}
	return 0;
}

https://www.luogu.com.cn/record/155276119

https://www.luogu.com.cn/record/155276131