B. Our Tanya is Crying Out Loud；题目

1特判，因为除1还是本身，这点就很淦

#include <bits/stdc++.h>
using namespace std;
#define int long long
vector<int> a((int)6e5);
vector<int> b((int)6e5), c[(int)6e5];
const int mod = 1e9 + 7;
signed main()
{int n, k, A, B;cin >> n >> k >> A >> B;if (k==1){cout<<(n-1)*A;return 0;}int res = 0;while (n > 1){if (n % k == 0)res += min((n - n / k) * A, B), n /= k;elseres += min((n % k), n - 1) * A, n -= min((n % k), n - 1);}cout << res << endl;
}