A. Counterexample （Codeforces Round #275(div2)

A. Counterexample

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

Your friend has recently learned about coprime numbers. A pair of numbers {a, b} is called coprime if
the maximum number that divides both a and b is
equal to one.

Your friend often comes up with different statements. He has recently supposed that if the pair (a, b) is coprime and the pair (b, c) is
coprime, then the pair (a, c) is coprime.

You want to find a counterexample for your friend's statement. Therefore, your task is to find three distinct numbers (a, b, c), for which
the statement is false, and the numbers meet the condition l ≤ a < b < c ≤ r.

More specifically, you need to find three numbers (a, b, c), such that l ≤ a < b < c ≤ r,
pairs (a, b) and (b, c) are coprime,
and pair (a, c)is not coprime.

Input

The single line contains two positive space-separated integers l, r (1 ≤ l ≤ r ≤ 1018; r - l ≤ 50).

Output

Print three positive space-separated integers a, b, c —
three distinct numbers (a, b, c) that form the counterexample. If there are several solutions, you are allowed to print any of them. The
numbers must be printed in ascending order.

If the counterexample does not exist, print the single number -1.

Sample test(s)

input

2 4

output

2 3 4

input

10 11

output

-1

input

900000000000000009 900000000000000029

output

900000000000000009 900000000000000010 900000000000000021

Note

In the first sample pair (2, 4) is not coprime and pairs (2, 3) and (3, 4) are.

In the second sample you cannot form a group of three distinct integers, so the answer is -1.

In the third sample it is easy to see that numbers 900000000000000009 and 900000000000000021 are
divisible by three.

找出3个数，前两个的最大公约数为1，后两个最大公约数为1，第1个和第3个的最大公约数不为1.

因为题目中说了。r-l<=50,能够直接O(n^3)暴力做。

代码：

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
long long gcd(long long a,long long b)
{
    return b==0?a:gcd(b,a%b);
}
int main()
{
    long long l,r;
    long long x,y,z;
    int sign=0;
    scanf("%I64d%I64d",&l,&r);
    for(long long i=l;i<=r;i++)
    {
        for(long long j=i+1;j<=r;j++)
        {
            for(long long k=j+1;k<=r;k++)
            {
                if(gcd(i,j)==1&&gcd(j,k)==1&&gcd(i,k)!=1)
                {
                    x=i;
                    y=j;
                    z=k;
                    sign=1;
                    break;
                }
            }
            if(sign)
            break;
        }
        if(sign)
        break;
    }
    if(sign)
    printf("%I64d %I64d %I64d\n",x,y,z);
    else
    printf("-1\n");
    return 0;
}