2014/7/19 codeforce div1A

http://codeforces.com/contest/449/problem/A
form WJMZBMR
 1 #include <iostream>
 2 #include <cstdio>
 3 #include <algorithm>
 4 #include <cstring>
 5 #include <string>
 6 using namespace std;
 7 
 8 typedef long long int64;
 9 
10 #define checkMax(a,b) a=max(a,b)
11 
12 
13 
14 int main() {
15     int n, m, k;
16     cin >> n >> m >> k;
17     if (n - 1 + m - 1 < k) {
18         puts("-1");
19         return 0;
20     }
21     int64 ans = 0;
22 //    int cnt = 0;
23     for (int64 i = 1; i <= n; i++) {
24 //        ++cnt;
25         int64 r = n / (n / i);
26         i = r;
27         if (k - (r - 1) > m - 1)
28             continue;
29         int64 o = max(k - (r - 1) + 1, 1LL);
30         checkMax(ans, 1LL * (n / r) * (m / o));
31         //cout << " " << z << " " << t << " " << tt << endl;
32     }
33 //    cout << cnt << endl;
34     cout << ans << endl;
35     return 0;
36 }