#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define REP(i,n) for(long (i)=0;(i)<(n);(i)++) #define FOR(i,a,b) for(long (i)=(a);(i)<(b);(i)++) #define RREP(i,a) for(long (i)=(a)-1;(i)>=0;(i)--) #define FORR(i,a,b) for(long (i)=(a)-1;(i)>=(b);(i)--) //#define MOD 1000000007 #define PI acos(-1.0) #define DEBUG(C) cout< #define PLL pair #define ALL(a) (a).begin(),(a).end() #define SORT(a) sort((a).begin(),(a).end()) #define RSORT(a) sort((a).begin(),(a).end(),greater()) typedef long long LL; typedef unsigned long long ULL; using namespace std; const LL MOD=1e9+7; int main(){ int N; cin>>N; ULL ans=0; ULL C,D; REP(i,N){ //cin>>C>>D; scanf("%lld %lld",&C,&D); D%=MOD; LL num=((C+1)/2)%MOD; num*=D; num%=MOD; ans+=num; ans%=MOD; } cout<