## Sum of largest prime factors

### Problem 642

Let $f(n)$ be the largest prime factor of $n$ and $\displaystyle F(n) = \sum_{i=2}^{n}f(i)$.

For example $F(10)=32$, $F(100)=1915$ and $F(10000)=10118280$.

Find $F(201820182018)$. Give your answer modulus $10^9$.