#include<bits/stdc++.h>
using namespace std;

using uint = unsigned int;
using ll = long long;

#define CIN( LL , A ) LL A; cin >> A 
#define GETLINE( A ) string A; getline( cin , A ) 
#define GETLINE_SEPARATE( A , SEPARATOR ) string A; getline( cin , A , SEPARATOR ) 
#define FOR_LL( VAR , INITIAL , FINAL_PLUS_ONE ) for( ll VAR = INITIAL ; VAR < FINAL_PLUS_ONE ; VAR ++ ) 
#define FOR_ITR( ARRAY , ITR , END ) for( auto ITR = ARRAY .begin() , END = ARRAY .end() ; ITR != END ; ITR ++ ) 
#define REPEAT( HOW_MANY_TIMES ) FOR_LL( VARIABLE_FOR_REPEAT , 0 , HOW_MANY_TIMES ) 
#define RETURN( ANSWER ) cout << ( ANSWER ) << endl; return 0 
#define DOUBLE( PRECISION , ANSWER ) cout << fixed << setprecision( PRECISION ) << ( ANSWER ) << endl; return 0 
#define MIN( A , B ) A < B ? A : B;
#define MAX( A , B ) A < B ? B : A;
template <typename T> inline T Distance( const T& a , const T& b ){ return a < b ? b - a : a - b; }

constexpr const ll P = 1000000007;

int main(){
  CIN( ll , N );
  ll answer = 0;
  FOR_LL( i , 0 , N ){
    CIN( ll , Ck );
    CIN( ll , Dk );
    ll num = ( Ck / 2 + ( Ck % 2 == 0 ? 0 : 1 ) ) % P;
    answer = ( answer + num * ( Dk % P ) ) % P;
  }
  RETURN( answer );
}