ZOJ 3665 Yukari's Birthday

#include <iostream>
#include <cstdio>
#include <cmath>
#define ll long long
using namespace std;
ll n,r;
ll pow1(ll mid,ll r)
{
    ll t=1;
    for(ll i=1;i<=r;++i)
    {
        t*=mid;
    }
    return t;
}
ll solve(ll low,ll high)
{
    if(low>high) return -1;
    else
    {
        ll mid=(low+high)/2;
        ll temp=mid*(1-pow1(mid,r))/(1-mid);
        if(temp==n||temp==n-1) return mid;
        else if(temp>n) return solve(low,mid-1);
        else return solve(mid+1,high);
    } 
    
}

int main()
{
    while (scanf("%lld",&n)!=EOF)
    {
        ll ansr=1;
        ll ansk=n-1;
        ll min=n-1;
        ll k,high;
       for(r=2;r<=42;++r)
        {
            high=(ll) pow(n+1.0,1.0/r)+1;
            k=solve(2,high);
            if(k!=-1)
            {
              if(k*r<min)
              {
                ansk=k;
                ansr=r;
              }
              if(k*r==min&&r<ansr)
              {
                    ansr=r;
                    ansk=k;
              }
            }
        }
        printf("%lld %lld\n", ansr, ansk);
    }
    return 0;
}