#include <stdio.h>

double ant ( double l )
{
    double t = 0, e = l, a = 0;

    while (1) {
        if (e - a <= 1) return t + (e - a);
        t += 1;
        a += 1;
        a *= (e + l) / e;
        e += l;
    }
}

int main ()
{
    double len;

    printf("Initial length of the rope: "); scanf("%lf", &len);
    printf("Ant reaches end of rope after %lf seconds\n", ant(len));
    return 0;
}