#include <bits/stdc++.h>
using namespace std;
const int N=1919810;
typedef long long ll;
typedef pair<ll,ll> PII;
ll n,y,b,d;
ll ans;

ll cal(ll a,ll jz){
    
    return a/100*jz*jz+(a/10)%10*jz+a%10;
}


bool gao3(ll x){
    ll nn=n,sum=0,item=1;
    while(nn){
        ll t=nn%x;
       // cout<<t<<endl;
        if(t>=10) return false;
        sum+=item*t;
        item*=10;
        nn/=x;
    }
   // cout<<sum<<endl;
    return sum>=y;
}

int main() {
	cin>>n>>y;
	ans=10;
	    for(ll i=y;i<1000;i++){//ans
	        
	            ll l=10,r=1e18;
              if(i>=100) r=1e9;
             while(l<r){
             ll mid=(l+r)>>1;
                if(cal(i,mid)>=n) r=mid;
              else l=mid+1;
            }
            if(cal(i,l)==n){
                //cout<<l<<endl;
               ans=max(l,ans); 
            } 
	            //return 0;
	        
	    }
	    
	b=1e6;    
	//gao3(41);
	while(b>=ans){
	    //cout<<b<<"\n";
	    if(gao3(b)){
	        ans=b;
	        break;
	    }
	    b--;
	}
	cout<<ans<<endl;
}