time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output
You are given several queries. In the i-th query you are given a single positive integer ni. You are to represent ni as a sum of maximum possible number of composite summands and print this maximum number, or print -1, if there are no such splittings.
An integer greater than 1 is composite, if it is not prime, i.e. if it has positive divisors not equal to 1 and the integer itself.
Input
The first line contains single integer q (1 ≤ q ≤ 105) — the number of queries.
q lines follow. The (i + 1)-th line contains single integer ni (1 ≤ ni ≤ 109) — the i-th query.
Output
For each query print the maximum possible number of summands in a valid splitting to composite summands, or -1, if there are no such splittings.
Examples
input
Copy
1
12
output
Copy
3
input
Copy
2
6
8
output
Copy
1
2
input
Copy
3
1
2
3
output
Copy
-1
-1
-1
Note
12 = 4 + 4 + 4 = 4 + 8 = 6 + 6 = 12, but the first splitting has the maximum possible number of summands.
8 = 4 + 4, 6 can't be split into several composite summands.
1, 2, 3 are less than any composite number, so they do not have valid splittings.
刚开始看错题了,我不知道是英语差,还是cf的英语表达有点奇怪,老是容易看错题,我都怀疑我的四六级是怎么过的,高中英语怎么学的。
刚开始以为是求合数之和等于n的方案数,自闭后才知道是求最多数的合数之和,那么就是一道水题了。
最小合数是4,那么就t=n/4若余数为0,t就是答案。
若余数为1,拿两个四与这个1组成9。
若余数为2,拿一个四组成6,
余数为3,拆成2和1拿一个四组成6,拿两个四组成9
AC代码:
#include<bits/stdc++.h>
using namespace std;
int cal(int n)
{
int t=n/4;
int yu=n%4;
if(yu==0) return t;
if(yu==1)
{
if(t>=2) return t-1;
else return -1;
}
if(yu==2) return t;
if(yu==3)
{
if(t>=3) return t-1;
else return -1;
}
}
int main()
{
int t;
cin>>t;
while(t--)
{
int n;cin>>n;
if(n<4) printf("-1\n");
else printf("%d\n",cal(n));
}
}