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 - ) / x != b) return false;
     }
     return true;
 }
 int main()
 {
     while (cin >> n >> m)
     {
         unordered_map<int, int> mp;
         for (int i = ; i < m; i++)
         {
             cin >> x >> y;
             mp[x] = y;
         }
         int ans = -;
         bool flg = true;
         for (int i = ; i <= ; i++)
         {
             if (check(i, mp))
             {
                 if (ans != - && (n + i - ) / i != ans)
                 {
                     flg = false; break;
                 }
                 else ans = (n + i - ) / i;
             }
         }
         if (flg && ans != -) cout << ans << endl;
         else cout << - << endl;
     }
     return ;
 }