#include<bits/stdc++.h>
using namespace std ;
int main(){
int a;
while(cin>>a){
if(a%2==0||a==0){
cout<<a<<endl;
}
else cout<<a-1<<endl;
}
return 0;
}
#include
using namespace std ;
int main(){
int a;
while(cin>>a){
if(a%2==0||a==0){
cout<
}
else cout<
}
return 0;
}
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