// yukicoder 312 (http://yukicoder.me/problems/847)
#include<cstdio>
#define rep(i,a) for(int i=0;i<(a);++i)

typedef long long ll;

ll N;

int main()
{
	scanf( "%lld", &N );

	for( ll i = 3; i*i <= N; ++i )
	{
		if( N % i == 0 )
		{ printf( "%d\n", i ); return 0; }
	}

	printf( "%lld\n", N );

	return 0;
}