#include <bits/stdc++.h>

int ri() {
	int n;
	scanf("%d", &n);
	return n;
}



int main() {
	int n = ri();
	if (n == 1) {
		puts("1.20205690315959428539973816151144");
	} else if (n == 2) {
		puts("1.0823232337111381915160036965411679027747");
	} else if (n == 3) {
		puts("1.036927755");
	} else if (n > 50) puts("1");
	else {
		long double res = 0;
		for (int b = 2; b <= 100; b++) {
			long double x = 1;
			for (int i = 0; i < n; i++) x *= (long double) 1 / b;
			res += (1 - x) / ((long double) b * (b - 1));
		}
		res += 0.01;
		
		for (int a = 2; a <= 400; a++) {
			long double cur = 0;
			for (int b = a + 1; b <= 1000; b++) {
				long double x = 1;
				for (int i = 0; i < n; i++) x *= (long double) a / b;
				cur += (1 - x) / ((long double) b * (b - a));
			}
			for (int i = 1; i <= a; i++) cur -= 1.0L / (1000 + i) / a;
			for (int i = 1; i <= n; i++) cur /= a;
			res += cur;
		}
		
		printf("%.11Lf\n", res);
		
	}
	
	return 0;
}