#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; #define reE(i,a,b) for(auto (i)=(a);(i)<=(b);(i)++) #define rE(i,b) reE(i,0,b) #define reT(i,a,b) for(auto (i)=(a);(i)<(b);(i)++) #define rT(i,b) reT(i,0,b) #define rep(i,a,b) reE(i,a,b); #define rev(i,a,b) for(auto (i)=(b)-1;(i)>=(a);(i)--) #define fe(i,b) for (auto &(x):b); #define itr(i,b) for(auto (i)=(b).begin();(i)!=(b).end();++(i)) #define rti(i,b) for(auto (i)=(b).rbegin();(i)!=(b).rend();++(i)) #define LL long long #define all(b) (b).begin(),(b).end() #define input_init stringstream ss; string strtoken, token; istringstream is #define input_line getline(cin, strtoken);is.str(strtoken);is.clear(istringstream::goodbit) #define input_token(num) ss.str(""); ss.clear(stringstream::goodbit); getline(is, token, ','); ss << token; ss >> num #define dir(xx,yy,x,y,i) (xx)=(x)+dir[(i)],(yy)=(y)+dir[(i)+1] typedef complex P; typedef vector

Poly; const int INF = 1 << 30; const double eps = 1e-8; const int dir[] = { 0, 1, 0, -1, 0 }; int t[10000000]; int o[2]; int maxi=0; int N,a,b; int main(void){ cin >> N; rT(i, N){ cin >> a >> b; t[i] = a + 4 * b; maxi = max(t[i], maxi); o[t[i] & 1]++; } if (o[0] > 0 && o[1] > 0){ cout << -1 << endl; return 0; } LL cnt = 0; rT(i, N){ cnt += (maxi - t[i]) / 2; } cout << cnt << endl; return(0); }