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

void print(vector<long long>& v){
    for(int i = v.size()-1; 0 <= i; --i) cout << v[i] << " ";
    cout << endl;
}
template <class T> void chmin(T& a, const T b){a=min(a,b);}

int main() {
    long long A,B,C; cin >> A >> B >> C;
    if(C==1 || C>=5000){
        cout << B*A << endl;
        return 0;
    }
    vector<long long> dp(A+1,A*B);
    dp[0] = 0;
    for(int i = 0; i < A; ++i){
        if(i*C<=A) chmin(dp[i*C],dp[i]+1);
        for(int j = 1; j < C && i+j <= A; ++j){
            chmin(dp[i+j],dp[i]+1);
        }
    }
    cout << dp[A]*B << endl;

    return 0;
}