C :

#include<stdio.h> 
int main()
{
    double n,i,s=0;
    scanf("%lf",&n); 
    for(i=1; i<=n ;i++)
    {
             s= s+1/i;
    }
    printf("%.3lf\n",s);
    return 0;
}

C++ :

#include <iostream>
#include <iomanip>
using namespace std;

int main(){
	int i,n;
	double s = 0;
	cin>>n;
	
	for(i = 1;i <= n;i++){
		s = s + 1.0 / i;
	} 
	cout<<fixed<<setprecision(3)<<s<<endl;
	
}

Python :

n =  int(input());
s = 0;
for i in range(1,n + 1):
    s = s + 1/i;
print('%.3f' % s);