#include using namespace std; typedef signed long long ll; #undef _P #define _P(...) (void)printf(__VA_ARGS__) #define FOR(x,to) for(x=0;x>N; FOR(i,N) cin>>X[i]>>Y[i]; FOR(x,N) FOR(y,N) { if(Y[x]==Y[y]) cr[x][y]=-1; cr[x][y] = (X[y]-X[x])*1.0/(Y[x]-Y[y]); } set S; S.insert(1); x=0; FOR(y,N) { if(X[y]xx && cr[x][y]=1e10) break; S.insert(mi); xx=mi; x=ne; } x=0; FOR(y,N) { if(X[y]>X[x]) x=y; else if(X[y]>=X[x] && Y[y]>Y[x]) x=y; } xx=0; while(1) { int ne=x; double mi=1e10; FOR(y,N) if(cr[x][y]>xx && cr[x][y]=1e10) break; S.insert(mi); xx=mi; x=ne; } ITR(it,S) val(*it-2),val(*it-1),val(*it),val(*it+1),val(*it+2); cout<