Submission #7423515

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Source Code Expand

#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <map>
#include <queue>
#include <cstdio>
#include <string.h>
#define rep(i,n) for (int i = 0; i < (int)n; i++)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pi;
typedef pair<pi, pi> pp;
typedef pair<ll, ll> pl;
double PI = 3.1415926535897932;
const double EPS = 1e-9;
const ll MOD = 1000000007;
const int inf = 1 << 30;
const ll linf = 1LL << 60;

ll N, A;
ll ans = linf;

int main() {
    cin >> N >> A;
    for (ll i = 1; i < 40; i++) {
        ll st = 0, en = 1000000000001;
        while (en-st > 1) {
            ll mid = (st + en) / 2;
            if (mid > inf && mid < N && i > 1) {
                en = mid;
                continue;
            }
            ll tmp = 1;
            rep(j,i) {
                tmp *= mid;
                if (tmp > N) break;
            }
            if (tmp >= N) en = mid;
            else st = mid;
        }
        ll b = en-1;
        ll cnt = i*b;
        ll tmp = 1;
        rep(j,i) tmp *= b;
        while (true) {
            tmp = (tmp/b) * (b+1);
            cnt++;
            if (tmp >= N) break;
        }
        ans = min(ans, A*(i-1)+cnt);
    }
    cout << ans << endl;
}

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