#include <stdlib.h>
#include <stdio.h>
int main(int argc, char* argv[]) {
int n = atoi(argv[1])-1;
int p = n/3;
int q = n/5;
int r = n/15;
int s = 3*((p*(p+1))/2) +
5*((q*(q+1))/2) -
15*((r*(r+1))/2);
printf("%d\n", s);
return 0;
}