A2. Collective Mindsets (medium)
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output
Way to go! Heidi now knows how many brains there must be for her to get one. But throwing herself in the midst of a clutch of hungry zombies is quite a risky endeavor. Hence Heidi wonders: what is the smallest number of brains that must be in the chest for her to get out at all (possibly empty-handed, but alive)?
The brain dinner night will evolve just as in the previous subtask: the same crowd is present, the N - 1 zombies have the exact same mindset as before and Heidi is to make the first proposal, which must be accepted by at least half of the attendees for her to survive.
Input
The only line of input contains one integer: N, the number of attendees (1 ≤ N ≤ 109).
Output
Output one integer: the smallest number of brains in the chest which allows Heidi to merely survive.
Examples
input
Copy
1
output
Copy
0
input
Copy
3
output
Copy
1
input
Copy
99
output
Copy
49找规律；
通过前16个可以发现：
奇数除以二就行了；
偶数有如下规律：
0 2
0 1 4 6
0 1 2 3 8 10 12 14
0 1 2 3 4 5 6 7 16 18 20 22 24 26 28 30
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <vector>
#include <map>
#include <string>
#include <queue>
using namespace std;
typedef long long ll;
int main()
{
int n;
while(cin >> n){
if(n%2==1)
cout << n/2 << endl;
else{
int ans = 1;
while(ans <= n){
ans *= 2;
}
cout << (n-ans/2)/2 <<endl;
}
}
return 0;
}