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

int main(){
    ll a, b, c, d;
    scanf("%lld %lld %lld.%lld", &a, &b, &c, &d);
    cout << (a + b) * ((c + 1) * 10 + d) / 10 << '\n';
}