#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

char*mmap();
#define rd(v) long v=0;{int _c;while(_c=*rp++-48,_c>=0)v=v*10+_c;}

#define wt_rev(v) {long _z=v;do*--wp=_z%10+48;while(_z/=10);}

main(){
	char*rp=mmap(0l,1l<<12,1,2,0,0ll);
	rd(n);
	long r;
	
	if(n%3==0){
		r=3;
		goto end;
	}
	if(n%4==0){
		r=4;
		goto end;
	}

	long e=sqrt(n);
	for(r=3;r<=e;r+=2){
		if(n%r==0){
			goto end;
		}
	}
	if(n%2==0){
		r=n/2;
		goto end;
	}
	r=n;
	
	end:;
	char wbuf[32],*wp=(wbuf+sizeof wbuf);
	wt_rev(r);
	write(1,wp,(wbuf+sizeof wbuf)-wp);
	_exit(0);
}