Problem 2

#include <stdio.h>

double power(double n) {
    double res = 2;
    for (int i = 1; i < n; i++) {
        res *= 2;
    }
    return res;
}

double series(double n) {
    if (n == 0) {
        return 1;
    }
    return (1.0 / power(n)) + series(n - 1);
}

int main() {
    double n;
    scanf("%lf", &n);

    printf("Sum = %.3lf\n", series(n));
}