#include <iostream>
using namespace std;
int numbers[] {2, 3, 5, 7, 11, 13, 17, 19};
string str = "";
int count = size(numbers);
for (int i = 0; i < count; i++) {
if (i % 2 == 1)
continue;
str += (str == "" ? "" : "-") +
to_string(numbers[i]);
}
//str is "2-5-11-17"
cout << "str is '" << str << "'";