Language: C++

#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <numeric>
#include <cmath>
#include <unordered_map>

using namespace std;
using ll = long long;

void _cin(){} template <class Head, class... Tail> void _cin(Head&& head, Tail&&... tail){ cin >> head; _cin(forward<Tail>(tail)...); }
void _cout(){ cout << "\n"; } template <class Head, class... Tail> void _cout(Head&& head, Tail&&... tail){ cout << head; _cout(forward<Tail>(tail)...); }
int gcd(int a, int b){ return (b == 0) ? a : gcd(b, a % b); }

#define Sq(x) (x)*(x)
#define For(i, n) for(int i = 0; i < (n); i ++)
#define Rep(n) For(_, n)
#define Range(c) c.begin(), c.end()
#define RevRange(c) c.rbegin(), c.rend()
#define Contains(c, x) (find(Range(c), x) != c.end())
#define Search(rb, re, x) distance(rb, find(rb, re, x))
#define Sort(a) sort(Range(a))
#define DeSort(a) sort(RevRange(a))
#define Reverse(c) reverse(Range(c))
#define Unique(a) a.erase(unique(Range(a)), a.end())
#define Cusum(T, xs, sxs) vector<T> sxs(xs.size()+1); For(i, (int)xs.size()) sxs[i+1] = sxs[i] + xs[i]
#define Cin(T, ...) T __VA_ARGS__; _cin(__VA_ARGS__)
#define Cins(T, n, xs) vector<T> xs(n); For(i, n) cin >> xs[i]
#define Cins2(T, n, xs, ys) vector<T> xs(n), ys(n); For(i, n) cin >> xs[i] >> ys[i]
#define Cins3(T, n, xs, ys, zs) vector<T> xs(n), ys(n), zs(n); For(i, n) cin >> xs[i] >> ys[i] >> zs[i]
#define Cinss(T, n, m, xs) Vec2(T, n, m, xs); For(i, n) For(j, m) cin >> xs[i][j]
#define Cinm(T, n, map) unordered_map<T, int> map; Rep(n){ Cin(T, x); map[x] ++; }
#define Cout(...) _cout(__VA_ARGS__)
#define Couts(xs) { for(const auto &e : xs) cout << e << " "; cout << "\n"; }
#define Coutyn(cond) Cout((cond) ? "yes" : "no")
#define CoutYn(cond) Cout((cond) ? "Yes" : "No")
#define CoutYN(cond) Cout((cond) ? "YES" : "NO")
#define vc vector
#define Mini(a, x) a = min(a, x)
#define Maxi(a, x) a = max(a, x)

// constexpr int MOD = 1e9+7;

int main(void){
    Cin(int, a, b, c, d);
    Cout(max{a+b, a-b, a*b});
}

Compiler output:
a.cc: In function 'int main()':
a.cc:47:13: error: expected ')' before '{' token
   47 |     Cout(max{a+b, a-b, a*b});
      |             ^
a.cc:34:25: note: in definition of macro 'Cout'
   34 | #define Cout(...) _cout(__VA_ARGS__)
      |                         ^~~~~~~~~~~
a.cc:34:24: note: to match this '('
   34 | #define Cout(...) _cout(__VA_ARGS__)
      |                        ^
a.cc:47:5: note: in expansion of macro 'Cout'
   47 |     Cout(max{a+b, a-b, a*b});
      |     ^~~~
a.cc:34:24: error: no matching function for call to '_cout(<unresolved overloaded function type>)'
   34 | #define Cout(...) _cout(__VA_ARGS__)
      |                        ^
a.cc:47:5: note: in expansion of macro 'Cout'
   47 |     Cout(max{a+b, a-b, a*b});
      |     ^~~~
a.cc:13:73: note: candidate: 'template<class Head, class ... Tail> void _cout(Head&&, Tail&& ...)'
   13 | void _cout(){ cout << "\n"; } template <class Head, class... Tail> void _cout(Head&& head, Tail&&... tail){ cout << head; _cout(forward<Tail>(tail)...); }
      |                                                                         ^~~~~
a.cc:13:73: note:   template argument deduction/substitution failed:
a.cc:34:24: note:   couldn't deduce template parameter 'Head'
   34 | #define Cout(...) _cout(__VA_ARGS__)
      |                        ^
a.cc:47:5: note: in expansion of macro 'Cout'
   47 |     Cout(max{a+b, a-b, a*b});
      |     ^~~~
a.cc:13:6: note: candidate: 'void _cout()'
   13 | void _cout(){ cout << "\n"; } template <class Head, class... Tail> void _cout(Head&& head, Tail&&... tail){ cout << head; _cout(forward<Tail>(tail)...); }
      |      ^~~~~
a.cc:13:6: note:   candidate expects 0 arguments, 1 provided