#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; inline int toInt(string s) { int v; istringstream sin(s); sin >> v; return v; } template inline string toString(T x) { ostringstream sout; sout << x; return sout.str(); } template inline T sqr(T x) { return x*x; } typedef pair P; typedef long long ll; typedef unsigned long long ull; #define For(i,a,b) for(int (i) = (a);i < (b);(i)++) #define rep(i,n) For(i,0,n) #define clr(a) memset((a), 0 ,sizeof(a)) #define mclr(a) memset((a), -1 ,sizeof(a)) #define all(a) (a).begin(),(a).end() #define rall(a) (a).rbegin(), (a).rend() #define sz(a) (sizeof(a)) #define Fill(a,v) fill((int*)a,(int*)(a+(sz(a)/sz(*(a)))),v) #define fi first #define se second bool cheak(int x, int y, int xMax, int yMax){ return x >= 0 && y >= 0 && xMax > x && yMax > y; } const int dx[4] = { -1, 0, 1, 0 }, dy[4] = { 0, 1, 0, -1 }; const int mod = 1000000007; const int INF = 30000 * 3; int main() { int n; cin >> n; set

s; int l = 20*20; rep(i, n){ int x, y; cin >> x >> y; bool f = false; For(tx,-20, 21)For(ty,-20,21){ if (s.count(P(tx,ty))) if(pow(x-tx,2)+pow(y-ty,2) < l){ f = true; break; } } if (f)continue; s.insert(P(x, y)); } cout << s.size() << endl; return 0; }