#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx")
#pragma GCC optimize("unroll-loops")
//#pragma warning(disable : 4996)

#ifdef _MSC_VER
#include <intrin.h>
#define __builtin_popcount __popcnt
#define __builtin_popcountll __popcnt64
#endif

#include <limits.h>
#include <math.h>
#include <time.h>

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <complex>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

using namespace std;

#define REP(i, n) for (int i = 0; i < (n); ++i)
#define REPR(i, n) for (int i = n - 1; i >= 0; --i)
#define FOR(i, m, n) for (int i = m; i < n; ++i)
#define FORR(i, m, n) for (int i = m - 1; i >= n; --i)
#define SORT(v, n) sort(v, v + n);
#define VSORT(v) sort(v.begin(), v.end());
#define REVERSE(v, n) reverse(v, v + n);
#define VREVERSE(v) reverse(v.begin(), v.end())
#define ll long long
#define print(x) cout << (x) << '\n'
#define pe(x) cout << (x) << " "
#define DEBUG(x) cout << #x << ": " << x << endl
#define lb(v, n) lower_bound(v.begin(), v.end(), (n))
#define ub(v, n) upper_bound(v.begin(), v.end(), (n))
#define int long long
#define double long double
#define all(x) (x).begin(), (x).end()
#define print_space(v) \
    REP(i, v.size()) cout << v[i] << " \n"[i == (int)v.size() - 1]
template <typename T1, typename T2>
inline void chmin(T1 &a, T2 b) {
    if (a > b) a = b;
}
template <typename T1, typename T2>
inline void chmax(T1 &a, T2 b) {
    if (a < b) a = b;
}
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;
std::random_device rd;
std::mt19937 mt(rd());
constexpr ll MOD = 1e9 + 7;
constexpr int MAX = 500050;
const double pi = acos(-1);
constexpr double EPS = 1e-8;
constexpr ll LINF = 1e18 + 1;
constexpr int INF = 1e9 + 1;

std::ostream &operator<<(std::ostream &dest, __int128_t value) {
    std::ostream::sentry s(dest);
    if (s) {
        __uint128_t tmp = value < 0 ? -value : value;
        char buffer[128];
        char *d = std::end(buffer);
        do {
            --d;
            *d = "0123456789"[tmp % 10];
            tmp /= 10;
        } while (tmp != 0);
        if (value < 0) {
            --d;
            *d = '-';
        }
        int len = std::end(buffer) - d;
        if (dest.rdbuf()->sputn(d, len) != len) {
            dest.setstate(std::ios_base::badbit);
        }
    }
    return dest;
}

void solve() {
    ll N, A;
    cin >> N >> A;
    __int128_t ans = LINF;
    REP(k, 41) {
        __int128_t ok = 0, ng = N + 1;
        while (abs(ok - ng) > 1) {
            __int128_t mid = (ok + ng) / 2;
            __int128_t res = 1;
            REP(_, k + 1) {
                res *= mid;
                if (res >= N) break;
            }
            if (res < N)
                ok = mid;
            else
                ng = mid;
        }
        __int128_t smax = ng;
        // DEBUG(k);
        // DEBUG(smax);
        REP(m, k + 1) {
            __int128_t res = k * A;
            __int128_t cnt = 1;
            REP(_, m) {
                if (cnt >= N) break;
                cnt *= (smax - 1);
            }
            REP(_, k + 1 - m) {
                if (cnt >= N) break;
                cnt *= smax;
            }
            res += smax * (k + 1 - m) + (smax - 1) * m;
            if (cnt >= N) { chmin(ans, res); }
        }
    }
    print(ans);
}

signed main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    // REP(_, 100)test();
    // int q;
    // cin >> q;
    // while (q--)
    solve();
}


Measured memory_bytes: 3656