Submission #856888

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Source Code Expand

#include <iostream>
#include <fstream>
#include <cstdio>
#include <cmath>
#include <vector>
#include <cstring>
#include <string>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <algorithm>
using namespace std;
 
#define REP(i,n) for(int i=0; i<n; ++i)
#define FOR(i,a,b) for(int i=a; i<=b; ++i)
#define FORR(i,a,b) for (int i=a; i>=b; --i)
#define pi M_PI
 
typedef long long ll;
typedef vector<int> VI;
typedef vector<ll> VL;
typedef vector<VI> VVI;
typedef pair<int,int> P;
typedef pair<ll,ll> PL;

ll f(ll b, ll n){
    if (n < b) return n;
    else return f(b, n/b) + (n%b);
}

int main() {
    ll n, s;
    cin >> n >> s;

    ll ans = -1;

    if (n == s){
        ans = n+1;
    }else if ((n+1)/2 < s){
        ans = -1;
    }else{
        FOR(i,2,sqrt(n)){
            if (f(i, n) == s){
                ans = i;
                break;
            }
        }
        if (ans == -1){
            for (ll i = sqrt(n-1); i>0; i--){
                ll x = (n+i)/(i+1);
                if (s > x) continue;
                ans = n/(i+1) + 1 + x - s;
                if (ans > n/i) continue;
                break;
            }
        }
    }

    cout << ans << endl;

    return 0;
}

Submission Info

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