i=int(input())
sum=0
if(i==2):
    sum+=2
elif(i>2):  
    sum+=2
    for j in range(3,i+1,2):
        if(j==3):
            sum+=3
        else:
            for k in range(3,int(j/2),2):
                if(j%k==0):
                    break
            else:
                sum+=j   
print(sum)