#include <iostream>
#include <iomanip>
#include <vector>
#include <string>

int main()
{
    unsigned num_lines;
    std::cout << "Enter the number of lines.\n> ";
    std::cin >> num_lines;

    const unsigned width = 79;
    std::vector<std::string> lines(num_lines);  // creates a vector of num_lines default constructed strings.

    for (unsigned i = 0; i < lines.size(); ++i)
        lines[i] = std::string((width / 2 ) - (i * 2 + 1)/2, ' ') + std::string(i * 2 + 1, '*');
    
    std::cout << '\n' ;
    for (unsigned i = 0; i < lines.size(); ++i)
        std::cout << lines[i] << '\n';
}