#include <cstdio>

struct Add {
	template<typename T>
	static auto eval(T lhs, T rhs) {
		return lhs + rhs;
	}
};

struct Mul {
	template<typename T>
	static auto eval(T lhs, T rhs) {
		return lhs * rhs;
	}
};

template<typename T>
class Value {
	T _value;

public:
	Value(T value): _value(value) {}

	auto eval() const { return _value; }
};

template<typename Op, typename LHS, typename RHS>
struct BinExpr {
	LHS lhs;
	RHS rhs;

	auto eval() const {
		return Op::eval(lhs.eval(), rhs.eval());
	}
};

int main() {
	using SubExpr = BinExpr<Mul, Value<int>, Value<int>>;
	using MyExpr  = BinExpr<Add, Value<int>, SubExpr>;

	int volatile v0 = 3, v1 = 5, v2 = 7;
	int result;

	MyExpr expr{{v0}, {{v1}, {v2}}};
	result = expr.eval();

	std::printf("%d\n", result);
}