Submission #855435

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Source Code Expand

#include <algorithm>
#include <cassert>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <iostream>
#include <vector>
#include <sstream>
#include <set>
using namespace std;
using ll = long long;

class range {private: struct I{int x;int operator*(){return x;}bool operator!=(I& lhs){return x<lhs.x;}void operator++(){++x;}};I i,n;
public:range(int n):i({0}),n({n}){}range(int i,int n):i({i}),n({n}){}I& begin(){return i;}I& end(){return n;}};

int main() {
  ll n, s;
  while (cin >> n >> s) {
    ll d = n - s;

    // brute force
    for (ll b = 2; b <= 1000000; ++b) {
      ll sum = 0, now = n;
      while (now > 0) {
        sum += now % b;
        now /= b;
      }
      if (sum == s) {
        cout << b << endl;
        goto NEXT;
      }
    }

    // b is big value
    if (d >= 1) {
      vector<ll> cands;
      for (ll i = 1; i * i <= d; ++i) {
        if (d % i == 0) {
          cands.push_back(i + 1);
          cands.push_back(d / i + 1);
        }
      }
      ll ret = 1LL << 60;
      for (auto cand : cands) {
        if (cand < 1000000) continue;
        ll sum = n / cand + n % cand;
        if (sum == s) ret = min(ret, cand);
      }
      cout << ((ret == (1LL << 60)) ? -1 : ret) << endl;
    } else if (d == 0) {
      cout << n + 1 << endl;
    } else {
      cout << -1 << endl;
    }

NEXT:;
  }
}

Submission Info

Judge Result