Codeforces Round #634 A. Candies and Two Sisters（水）

题目描述

There are two sisters Alice and Betty. You have n n n candies. You want to distribute these n n n candies between two sisters in such a way that:

• Alice will get a a a ( a>0 a > 0 a>0 ) candies;
• Betty will get b b b ( b>0 b > 0 b>0 ) candies;
• each sister will get some integer number of candies;
• Alice will get a greater amount of candies than Betty (i.e. a>b a > b a>b );
• all the candies will be given to one of two sisters (i.e. a+b=n a+b=n a+b=n ).

Your task is to calculate the number of ways to distribute exactly n n n candies between sisters in a way described above. Candies are indistinguishable.

Formally, find the number of ways to represent n n n as the sum of n=a+b n=a+b n=a+b , where a a a and b b b are positive integers and a>b a>b a>b .

You have to answer t t t independent test cases.

输入格式

The first line of the input contains one integer t t t ( 1≤t≤104 1 \le t \le 10^4 1≤t≤104 ) — the number of test cases. Then t t t test cases follow.

The only line of a test case contains one integer n n n ( 1≤n≤2⋅109 1 \le n \le 2 \cdot 10^9 1≤n≤2⋅109 ) — the number of candies you have.

输出格式

For each test case, print the answer — the number of ways to distribute exactly n n n candies between two sisters in a way described in the problem statement. If there is no way to satisfy all the conditions, print 0 0 0 .

输入输出样例

输入 #1 复制

6
7
1
2
3
2000000000
763243547

输出 #1 复制

3
0
0
1
999999999
381621773

输出(n-1)/2即可。

#include <bits/stdc++.h>
using namespace std;
int main()
{
    int t;
    cin>>t;
    while(t--)
    {
        long long n;
        scanf("%lld",&n);
        cout<<(n-1)/2;
    }
    return 0;
}