#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; //conversion //------------------------------------------ inline int toInt(string s) {int v; istringstream sin(s);sin>>v;return v;} template inline string toString(T x) {ostringstream sout;sout< inline T sqr(T x) {return x*x;} //typedef //------------------------------------------ typedef vector VI; typedef vector VVI; typedef vector VS; typedef pair PII; typedef long long LL; //container util //------------------------------------------ #define ALL(a) (a).begin(),(a).end() #define RALL(a) (a).rbegin(), (a).rend() #define PB push_back #define MP make_pair #define SZ(a) int((a).size()) #define EACH(i,c) for(typeof((c).begin()) i=(c).begin(); i!=(c).end(); ++i) #define EXIST(s,e) ((s).find(e)!=(s).end()) #define SORT(c) sort((c).begin(),(c).end()) //repetition //------------------------------------------ #define FOR(i,a,b) for(int i=(a);i<(b);++i) #define REP(i,n) FOR(i,0,n) //constant //-------------------------------------------- const double EPS = 1e-10; const double PI = acos(-1.0); //clear memory #define CLR(a) memset((a), 0 ,sizeof(a)) //debug #define dump(x) cerr << #x << '=' << (x) << endl; #define debug(x) cerr << #x << '=' << (x) << '('<<'L' << __LINE__ << ')' << ' ' << __FILE__ << endl; int main(){ int N; LL C,D; LL num=0; cin>>N; LL mod=(1e+9)+7; REP(i,N){ cin>>C>>D; LL a=C/2+C%2; a%=mod; num+=a*(D%mod); } cout<