# Problem 521: Smallest prime factor
Let smpf(n) be the smallest prime factor of n. smpf(91)=7 because
91=7×13 and smpf(45)=3 because 45=3×3×5. Let S(n) be the sum of smpf(i)
for 2 ≤ i ≤ n. E.g. S(100)=1257. Find S(1012) mod 109.