#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define drep(i, cc, n) for (ll i = (cc); i <= (n); ++i)
#define rep(i, n) drep(i, 0, n - 1)
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define fi first
#define se second

const ll MOD = 1000000007;
const ll MOD2 = 998244353;
const ll INF = 1LL << 60;
const ll MAX_N = 2e5;

int main(){
    ll n, a, b;
    cin >> n >> a >> b;

    if(a < b){
        cout << a*(n-1) - b*n << endl;
    }else{
        cout << -a*(n-1) - b*(n+1)/2 + b*(n/2) << endl;
    }
}