'''
Problem Statement:
If we list all the natural numbers below 10 that are multiples of 3 or 5,
we get 3,5,6 and 9. The sum of these multiples is 23.
Find the sum of all the multiples of 3 or 5 below N.
'''
n = int(raw_input().strip())
sum=0;
for a in range(3,n):
    if(a%3==0 or a%5==0):
        sum+=a
print sum;