C++ variadic sum

sum.cpp

#include <iostream>

template<typename T>
int sum(T v) {
    return v;
}

template<typename T, typename... Types>
int sum(T v, Types&&... others) {
    return v + sum(others...);
}

int main() {
    int a = sum(5, 7, 9);
    int b = sum(2);
    int c = sum(42, 14, 2, 18, 9);

    std::cout << a << ' ' << b << ' ' << c << '\n';
        
    return 0;
}