Google Kick Start 2021 Round E - D(Increasing Sequence Card Game)

#include <bits/stdc++.h>
using namespace std;

int main() {
	int T;
	scanf("%d", &T);
	
	for(int tc = 1; tc <= T; tc++) {
		unsigned long long N;
		scanf("%llu", &N);
		
		long double one = 1;
		if(N <= 1000000) {
			long double result = 0;
			
			for(int i = 1; i <= N; i++)
				result += one/(long double)(i);
			
			printf("Case #%d: %.19Lf\n", tc, result);
			continue;
		}
		long double result = 0;
			
		for(int i = 1; i <= 1000000; i++)
			result += one/(long double)(i);
		
		result += log(N+1)-log(1000001);
		printf("Case #%d: %.19Lf\n", tc, result);
	}
}