define FOR(i, n) for(int i = 0; i < n; i++)

int gcd(int a, int b) {
    while(b != 0) {
    int n = b;
    b = a % b;
    a = n;
    }
    return a;
}

Just practising some ~\LaTeX~

~e^{i\theta} = i\sin\theta + \cos\theta~