using namespace std;
#include <bits/stdc++.h>
#define _ ios_base::sync_with_stdio(0);cin.tie(0);
#define __ return EXIT_SUCCESS;
#define FOR(I,A,B) for(int I=A;I<B;I++)
#define ALL(C) C.begin(), C.end()
#define MYGC(C) (C)=getchar_unlocked()
#define MYPC(C) putchar_unlocked(C)
void reader(int *x){int k,m=0;*x=0;for(;;){MYGC(k);if(k=='-'){m=1;break;}if('0'<=k&&k<='9'){*x=k-'0';break;}}for(;;){MYGC(k);if(k<'0'||k>'9')break;*x=(*x)*10+k-'0';}if(m)(*x)=-(*x);}
void writer(int x, char c){int s=0,m=0;char f[10];if(x<0)m=1,x=-x;while(x)f[s++]=x%10,x/=10;if(!s)f[s++]=0;if(m)MYPC('-');while(s--)MYPC(f[s]+'0');MYPC(c);}
int main()
{
	_
	int N;
	reader(&N);
	if(!(N%2))writer(N,'\n');
	else writer(N+1,'\n');
	__
}