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

#define rd() ({long _v=0,_c;while(_c=*rp++-48,_c>=0)_v=_v*10+_c;_v;})
#define wt(v) {ulong _z=v;do*--wp=_z%10+48;while(_z/=10);}
#define rrep(v,e) for(long v=e;v--;)
#define chmax(v,a) (v=v>=a?v:a)

typedef unsigned long ulong;

int main(){
	char*mmap();
	char*rp=mmap(0l,1l<<25,1,2,0,0ll);
	long n=rd();
	long z=-1;
	rrep(i,n){
		if(rp[i]&1){
			z+=2;
			chmax(z,n-i);
		}
	}
	char wbuf[64],*wp=wbuf+sizeof wbuf;
	wt(z);
	write(1,wp,wbuf+sizeof wbuf-wp);
	_exit(0);
}