#include <stdio.h>

double my_power(int base, int n) {
	double total = base;
	for (int i = 1; i < n; i++) {
		total *= base;
	}
	return total;
}

double sum_sequence(int n) {
	double sum = 0.0;
	for (int i = 2*n; i > 0; i--) {
		double val = 1/my_power(i, i);
		if (i % 2 == 0) {
			sum -= val;
		} else {
			sum += val;
		}
	}
	return sum;
}

int main(int argc, char* argv[]) {
	printf("Enter n: ");
	int n;
	scanf("%d", &n);
	printf("Sum sequence = %f\n", sum_sequence(n));
	return 0;
}