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

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

	return 0;
}