decltype(x) Versus decltype((x))

1#include <iostream>
2 
3int main() {
4    int x = 5;
5    decltype(x) a = x;
6    decltype((x)) b = x;
7    std::cout << x << " " << a << " " << b << "\n";
8    a = 50;
9    std::cout << x << " " << a << " " << b << "\n";
10    b = 7;
11    std::cout << x << " " << a << " " << b << "\n";
12    return 0;
13}