Language: C++

#include <bits/stdc++.h>
using namespace std;

#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define rep(i, x, y)   for (__typeof(x) i = x; i < y; i++)
#define repr(i, x, y)   for (__typeof(x) i = x; i > y; i --)
#define endl "\n"
#define all(x)                      (x).begin(),(x).end()
#define Sort(x)                     sort(all((x)))
#define rSort(x)                     sort((x).rbegin(),(x).rend())
#define X                           first
#define Y                           second
#define sep                         ' '
#define SZ(x)                       ll(x.size())
#define MAX(a,b) ((a)>(b)?(a):(b))
#define MIN(a,b) ((a)<(b)?(a):(b))
#define pb                          push_back
#define mp                          make_pair
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> pll;
typedef pair<double, double> pdd;
typedef vector<ll> vll;
#define first X
#define second Y

const ll N = 1e6 + 7;
const ll M = 1e17 + 7;


int32_t main()
{
     IOS;
     ll n;
     double m;
     cin >> n >> m;
  		#include <bits/stdc++.h>
using namespace std;

#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define rep(i, x, y)   for (__typeof(x) i = x; i < y; i++)
#define repr(i, x, y)   for (__typeof(x) i = x; i > y; i --)
#define endl "\n"
#define all(x)                      (x).begin(),(x).end()
#define Sort(x)                     sort(all((x)))
#define rSort(x)                     sort((x).rbegin(),(x).rend())
#define X                           first
#define Y                           second
#define sep                         ' '
#define SZ(x)                       ll(x.size())
#define MAX(a,b) ((a)>(b)?(a):(b))
#define MIN(a,b) ((a)<(b)?(a):(b))
#define pb                          push_back
#define mp                          make_pair
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> pll;
typedef pair<double, double> pdd;
typedef vector<ll> vll;
#define first X
#define second Y

const ll N = 1e6 + 7;
const ll M = 1e17 + 7;


int32_t main()
{
     IOS;
     ll n,m2;
     double m;
     cin >> n >> m;
     
     m*=100;
  	 m2=m;
  	 ll ans= n*m2;
     //cout << ans << sep;
     
     cout << ans/100<<endl;
     //cout << (9888666969998*96)/100+9888666969998;
     
}

    
     
     
    
     u%=100;
     //cout << u << endl;
     ll cnt=(n*u)/100;
     ans+=cnt;
     cout << ans<<endl;
     //cout << (9888666969998*96)/100+9888666969998;
     
}


Compiler output:
a.cc: In function 'int32_t main()':
a.cc:67:13: warning: empty parentheses were disambiguated as a function declaration [-Wvexing-parse]
   67 | int32_t main()
      |             ^~
a.cc:67:13: note: remove parentheses to default-initialize a variable
   67 | int32_t main()
      |             ^~
      |             --
a.cc:67:13: note: or replace parentheses with braces to value-initialize a variable
a.cc:68:1: error: a function-definition is not allowed here before '{' token
   68 | {
      | ^
a.cc:88:6: error: 'u' was not declared in this scope
   88 |      u%=100;
      |      ^
a.cc:91:6: error: 'ans' was not declared in this scope; did you mean 'abs'?
   91 |      ans+=cnt;
      |      ^~~
      |      abs