I have tried 20-30 times , using floor() and type casting but I can't seem to get AC. What is the problem here? Thanks for the help.

Problem : https://atcoder.jp/contests/abc169/tasks/abc169_c

// Author : Epsilon573
// If it works, don't touch it.

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

typedef long long ll;
typedef long double ld;

int main()
{
    ios_base :: sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    ll a; ld b;
    cin >> a >> b;

    ll c = b*100;

    cout << a*c/100LL;

    return 0;
}