/*
Problem:
Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2,
the first 10 terms will be:
1,2,3,5,8,13,21,34,55,89,..
By considering the terms in the Fibonacci sequence whose values do not exceed n, find the sum of the even-valued terms.
e.g. for n=10, we have {2,8}, sum is 10.
*/
#include <stdio.h>

int main() {
	int n = 0;
	int sum = 0;
	int i = 1;
	int j = 2;
	int temp;
	scanf("%d", &n);

	while (j <= n) {
		if ((j & 1) == 0) //can also use(j%2 == 0)
			sum += j;
		temp = i;
		i = j;
		j = temp + i;
	}

	printf("%d\n", sum);
}