int gcd(int m, int n)
{
        int tmp;
        while(m) { tmp = m; m = n % m; n = tmp; }       
        return n;
}

int lcm(int m, int n)
{
        return m / gcd(m, n) * n;
}

int main()
{
        printf(, lcm(21,35));
        return 0;
}