1bb

#include <iostream>
#include <math.h>
using namespace std;
int main()
{
    double e;
    cout << "vvedite e\n";
    cin >> e;
    double sum = 0;
    double a = e;
    int n = 1;
    while(fabs(a) >= e)
    {
        double f = 1;
		for(int i = 0; i < n; i++)
        	f *= 2;
		double s = 1;
		for(int i = 0; i < n; i++)
        	s *= 3;
        a = (double) f / s;
        sum += a;
        n++;
    }
    cout << sum;
    return 0;
}