Submission #3383886

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Source Code Expand

#include<bits/stdc++.h>
using namespace std;
template<typename T>inline void read(T &x)
{
	x=0;
	static int p;p=1;
	static char c;c=getchar();
	while(!isdigit(c)){if(c=='-')p=-1;c=getchar();}
	while(isdigit(c)) {x=(x<<1)+(x<<3)+(c-'0');c=getchar();}
	x*=p;
}
long long n,s;
long long f(long long b,long long j)
{
	if(j<b)return j;
	return f(b,j/b)+j%b;
}
int main()
{
	read(n);read(s);
	if(s==n)return printf("%lld\n",n+1),0;
	long long S=sqrt(n)+1;
	for(int i=2;i<=S;i++)
		if(f(i,n)==s)return printf("%d\n",i),0;
	long long ans=1e11+1;
	for(long long i=1;i*i<=n-s;i++)
		if((n-s)%i==0&&f((n-s)/i+1,n)==s)ans=min(ans,(n-s)/i+1);
	if(ans==1e11+1) puts("-1");
	else printf("%lld\n",ans);
	return 0;
}

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