#include <stdio.h>

double solve(const double a, const double n) {
    double temp = a;
    double result = 1.0 / a;
    for (int i = 1; i <= n; i += 1) {
        temp *= (a + i);
        result += 1.0 / temp;
    }
    return result;
}

int main() {
    double a = 1, n = 2;
    printf("%.3f\n", solve(a, n));
}