GCD and LCM Formula

GCD Function:
ll gcd(ll a , ll b)
{
    if(b<a) swap(a,b);
//    if(a == 0) return b;

    while(a > 0){
        ll mod = b%a;   /// mod<a
        b = a;
        a = mod;
    }

    return b;
}

LCM Function:
long long lcm(ll a , ll b)
{
    long long ans = 1LL*a*b;
    ans = ans/gcd(a,b);
    return ans;
}