//小G定义了两个函数F(n)为n的约数和,G(n)为F(1)+F(2)+...+F(n-1)+F(n) ll G(ll x){ ll res=0; for(ll i=1;i<=x;) { ll r = x/(x/i); res += (x/i) * (r + i) * (r - i + 1) / 2 ; i=r+1; } return res; }
//小G定义了两个函数F(n)为n的约数和,G(n)为F(1)+F(2)+...+F(n-1)+F(n) ll G(ll x){ ll res=0; for(ll i=1;i<=x;) { ll r = x/(x/i); res += (x/i) * (r + i) * (r - i + 1) / 2 ; i=r+1; } return res; }