Language: C++

#include <iostream>
#include<iomanip>
#include<cmath>
#include<vector>
#include<algorithm>
#include<string>
#include<deque>
#include<stack>
#include<map>
#include <random>
#include<queue>
#include<iterator>
#include <bitset>
#include <unordered_set>
#include<set>

using namespace std;
#define ll long long
#define endl "\n"
const int dx[] = { -1 , -1 , -1 , 0 , 0 , 0 , 1 , 1 , 1 };
const int dy[] = { -1 , 0 , 1 , -1 , 0 , 1 , -1 , 0 , 1 };
const ll integer = pow(2, 32) - 1; // 4294967295
#define N 8010000
#define TC int t;cin>>t;for(int T=1;T<=t;T++)
#define mod 1000000007
#define PI acos(-1)
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
void AIA() { ios::sync_with_stdio(0); cin.tie(0); cout.tie(0); }
//cout<<fixed<<setprecision(20);
// freopen("stand.in","r",stdin);
// freopen("stand.out","w",stdout);

/*
 _____________              __                ___        ___       ___________________________     ____        ____
|             |            /\ \              |   |      |   |     |                           |    \   \      /   /
|   __________|           / /\ \             |   |      |   |     |      _____      _____     |     \   \    /   /
|  |                     / /  \ \            |   |      |   |     |     |     |    |     |    |      \   \  /   /
|  |                    / /    \ \           |   |      |   |     |     |     |    |     |    |       \   \/   /
|  |______             / /      \ \          |   |______|   |     |     |     |    |     |    |        \      /
|         |           / /        \ \         |              |     |     |     |    |     |    |         \    /
|   ______|          / /          \ \        |    ______    |     |     |     |    |     |    |          |  |
|  |                / /============\ \       |   |      |   |     |     |     |    |     |    |          |  |
|  |               / /==============\ \      |   |      |   |     |     |     |    |     |    |          |  |
|  |              / /                \ \     |   |      |   |     |     |     |    |     |    |          |  |
|  |             / /                  \ \    |   |      |   |     |     |     |    |     |    |          |  |
|__|            /_/                    \_\   |___|      |___|     |_____|     |____|     |____|          |__|

										  <<<<<<<<<<< NEVER GIVE UP !! >>>>>>>>>>>
										<<<<<<<< YOU CAN DO IT IF YOU WANT !! >>>>>>>>
										 <<<<<<<<< BELIEVE IN YOURSELF !! >>>>>>>>>

*/
string tis(int n) {
	string num="";
	while (n > 0) {
		num = char((n % 10)+'0') + num;
		n /= 10;
	}
	return num;
}
ll tin(string s) {
	ll re = 0;
	for (int i = 0; i < s.size(); i++) {
		re *= 10;
		re += int(s[i] - '0');
	}
	return re;
}
const ll ex = 1e18;
int main()
{
	//cout << fixed << setprecision(6);
	//freopen("stand.in","r",stdin);
	//freopen("stand.out","w",stdout);
	AIA();
	ll a;
	double b;
	cin >> a >> b;
	cout << ll(a * b);
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:18:12: error: expected primary-expression before 'long'
   18 | #define ll long long
      |            ^~~~
a.cc:80:17: note: in expansion of macro 'll'
   80 |         cout << ll(a * b);
      |                 ^~