проверить

#include<iostream>
#include <cmath>
using namespace std;
int main()
{
	int n, i = 1;
	float e, s = 0, b = 1/3;
	cout << "e="; cin >> e;
	while (fabs(b)>= e)
	{
		s += -1; i++;
		b / pow(3, 2 * i - 1);
	}
	cout << "s=" << s << endl;
	system("pause");
	return 0;
}