#include using namespace std; #define int long long typedef long long ll; typedef pairpint; typedef vectorvint; typedef vectorvpint; #define pb push_back #define mp make_pair #define fi first #define se second #define all(v) (v).begin(),(v).end() #define rep(i,n) for(int i=0;i<(n);i++) #define reps(i,f,n) for(int i=(f);i<(n);i++) #define each(it,v) for(__typeof((v).begin()) it=(v).begin();it!=(v).end();it++) templateinline void chmin(T &t,U f){if(t>f)t=f;} templateinline void chmax(T &t,U f){if(t>N; mapcnt; rep(i,2*N)cin>>A[i],cnt[A[i]]++;; sort(A,A+2*N); int D=0,W=0,M=0; each(it,cnt){ if(it->fi<0)continue; if(it->fi==0)M+=it->se/2; else M+=min(it->se,cnt[-it->fi]); } int l=0,r=2*N-1; for(;;r--){ while(l=r)break; l++; W++; } l=0;r=2*N-1; for(;;l++){ while(l=0)r--; if(l>=r)break; r--; D++; } cout<