#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
using namespace std;
using ll = long long ;
using P = pair<int,int> ;
using pll = pair<long long,long long>;
constexpr int INF = 1e9;
constexpr long long LINF = 1e17;
constexpr int MOD = 1000000007;
constexpr double PI = 3.14159265358979323846;

int main(){
    int v1,v2,t;
    scanf("%d.%d%d",&v1,&v2,&t);
    v2 += v1 * 10000;
    int ans = v2 * t;
    ans /= 10000;
    cout << ans << endl;
    return 0;
}