#include #include #include #include #include #include #include #include #include #include #include #include #define vll vector #define vvvl vector #define vvl vector> #define VV(a, b, c, d) vector>(a, vector(b, c)) #define VVV(a, b, c, d) vector(a, vvl(b, vll (c, d))); #define re(c, b) for(ll c=0;c> n; ll ans = 0; ll P = 1000000007; re(i, n){ ll a, b;std::cin >> a >> b; ll num = (a+1)/2; ans = (ans + ((num*b)%P))%P; } std::cout << ans << '\n'; }