CF861B Which floor?

思路：

暴力枚举。

实现：

#include <bits/stdc++.h>
using namespace std;
int n, m, x, y;
bool check(int x, unordered_map<int, int>& m)
{
    for (auto it : m)
    {
        int a = it.first, b = it.second;
        if ((a + x - 1) / x != b) return false;
    }
    return true;
}
int main()
{
    while (cin >> n >> m)
    {
        unordered_map<int, int> mp;
        for (int i = 0; i < m; i++)
        {
            cin >> x >> y;
            mp[x] = y;
        }
        int ans = -1;
        bool flg = true;
        for (int i = 1; i <= 100; i++)
        {
            if (check(i, mp))
            {
                if (ans != -1 && (n + i - 1) / i != ans)
                {
                    flg = false; break;
                }
                else ans = (n + i - 1) / i;
            }
        }
        if (flg && ans != -1) cout << ans << endl;
        else cout << -1 << endl;
    }
    return 0;
}