Codeforces Round #634 (Div. 3)

problem: (A) Candies and Two Sisters

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

Alice will get a (a>0) candies;
Betty will get b (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);
all the candies will be given to one of two sisters (i.e. a+b=n).
Your task is to calculate the number of ways to distribute exactly n candies between sisters in a way described above. Candies are indistinguishable.

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

You have to answer t independent test cases.

Input
The first line of the input contains one integer t (1≤t≤104) — the number of test cases. Then t test cases follow.

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

Output
For each test case, print the answer — the number of ways to distribute exactly 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.

Example
input
6
7
1
2
3
2000000000
763243547
output
3
0
0
1
999999999
381621773

代码

#include <iostream>
#include <stdio.h>
#include <string.h>
#include <algorithm>
using namespace std;
/*int max(int x,int y)
{
    return x>y?x:y;
}*/
int main()
{
    int t;
    long long int n;
    scanf("%d",&t);
    while (t--)
    {
        scanf("%lldd",&n);
        if(n<3) printf("%d\n",0);
        else if(n%2==0) printf("%d\n",(n/2)-1);
        else printf("%d\n",n/2);
    }
    return 0;
}