Dev - C++ - Como hacer este programa

#include <iostream>

using namespace std;

int main(int argc, char *argv[]) {

	int N;

	double suma = 0.0 , mult = 0.0, prom = 0.0;

	cin>> N;

	for (int i=1 ; i<N ; i++){

		suma = 1/i;

		suma = (suma + 1/i+1);

	}

	cout<< suma<<endl;

	for (int j = 1;j<N ; j++) {

		mult = 1/j;

		mult = mult*(1/j);

	}

	cout<<mult<<endl;

	for (int k=1 ; k<N ; k++){

		prom = 1/k;

		prom = (prom + 1/k+1)/N;

	}

	cout<< prom<<endl;

	return 0;

}

#include <stdio.h>

int main(void)

{

    double suma = 0.0;

    double prod = 1.0;

    int num;

    printf("Type an integer and press Enter: ");

    scanf("%d", &num);

    for (int i = 1; i <= num; ++i)

    {

        suma += 1.0 / (double) i;

        prod *= 1.0 / (double) i;

    }

    printf(

        "\nSum, product and average of reciprocals are:\n"

        "%.16g\n%.16g\n%.16g\n", suma, prod, suma / (double) num

    );

    return 0;

}

#include <iostream>

#include <iomanip>

int main()

{

    double suma = 0.0;

    double prod = 1.0;

    int num;

    std::cout << "Type an integer and press Enter: ";

    std::cin >> num;

    for (int i = 1; i <= num; ++i)

    {

        suma += 1.0 / static_cast<double>(i);

        prod *= 1.0 / static_cast<double>(i);

    }

    std::cout << "\nSum, product and average of reciprocals are:\n"

              << std::setprecision(16)

              << suma << '\n'

              << prod << '\n'

              << suma / static_cast<double>(num) << '\n';

    return 0;

}