Submission #993487

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Source Code Expand

#include <iostream>
#include <vector>
#include <algorithm>
#include <array>
#include <set>
#include <map>
#include <queue>
#include <tuple>
#include <unordered_set>
#include <unordered_map>
#include <functional>
#include <cassert>
#define repeat(i,n) for (int i = 0; (i) < (n); ++(i))
#define repeat_from(i,m,n) for (int i = (m); (i) < (n); ++(i))
#define repeat_reverse(i,n) for (int i = (n)-1; (i) >= 0; --(i))
#define repeat_from_reverse(i,m,n) for (int i = (n)-1; (i) >= (m); --(i))
#define whole(f,x,...) ([&](decltype((x)) whole) { return (f)(begin(whole), end(whole), ## __VA_ARGS__); })(x)
typedef long long ll;
using namespace std;
template <class T> void setmax(T & a, T const & b) { if (a < b) a = b; }
template <class T> void setmin(T & a, T const & b) { if (b < a) a = b; }
template <typename T, typename X> auto vectors(T a, X x) { return vector<T>(x, a); }
template <typename T, typename X, typename Y, typename... Zs> auto vectors(T a, X x, Y y, Zs... zs) { auto cont = vectors(a, y, zs...); return vector<decltype(cont)>(x, cont); }
template <typename T> T input(istream & in) { T a; in >> a; return a; }
const int inf = 1e9+7;
int main() {
    ll n, a; cin >> n >> a;
    assert (n <= 1000000);
    assert (a <= 1000000);
    vector<ll> dp(n+1, inf);
    repeat (i,n+1) {
        dp[i] = i;
        if (i) setmin(dp[i], dp[i-1]+1);
        auto f = [&](int x) { return dp[x] + a + dp[(i+x-1)/x]; };
        repeat_from (x,1,i) {
            setmin(dp[i], f(x));
            // cerr << "n = " << i << ", x = " << x << ": f = " << f(x) << endl;
            if (f(x) < f(x+1)) break; // ?????
        }
        // cerr << i << ' ' << dp[i] << endl;
    }
    cout << dp[n] << endl;
    return 0;
}

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