HackerEarth Coprimes problem solution

In this HackerEarth Coprimes problem solution, You are provided an integer n. Your task is to determine the largest integer a (a < n - 1) that is coprime of n. This implies that gcd(a,n) = 1.

HackerEarth Coprimes problem solution.

#include <bits/stdc++.h>

typedef long double ld ;
#define long long long int
using namespace std;
#define mp make_pair
#define pb push_back
#define x first
#define y second
typedef pair<long,long> pll; 

const int N=1e5+1;

long GCD(long a,long b)
{
    while(a && b)
    {
        a=a%b;
        if(a)
            b=b%a;
    }
    return a+b;
}

int main()
{
    ios::sync_with_stdio(false);cin.tie(0);
    srand(time(NULL));

    int t=1;
    while(t--)
    {
        long n;
        cin>>n;
        assert(3<=n && n<=1e18);

        if(n&1)
            cout<<n-2<<"\n";
        else
        {
            long temp=2;
            while(true)
            {
                long temp_gcd=GCD(n,n-temp);
                if(temp_gcd==1)
                {
                    cout<<n-temp<<"\n";
                    break;
                }
                temp++;
            }
        }

    }

    return 0;
}

Second solution

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn = 2e6 + 17;
 
ll n;
int main(){
    ios::sync_with_stdio(0), cin.tie(0);
    cin >> n;
    if(n % 2 == 0){
        for(int i = n - 3; ; i -= 2)
            if(gcd(n, i) == 1){
                cout << i << '\n';
                break;
            }
    }
    else
        cout << n - 2 << '\n';
}