#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(){
    ll v,t,p;
    cin >> v >> t >> p;
    
    if(v%t==0){
        cout << (((p+1)*(v/t)*(t+1)) + 2) << endl;
    }else{
        ll k = v/t + 1;
        cout << ((p+1)*(v+k)) << endl;
    }

    return 0;
}