import std;

void main() {
    int L;
    readf("%d\n", L);

    ulong M = 10 ^^ 9 + 7;

    ulong res = 1;
    foreach (_; 0 .. L) {
        ulong P, e;
        readf("%d %d\n", P, e);

        if (res == 0) continue;

        ulong inv = powmod(P-1, M-2, M);
        ulong num = powmod(P, e+2, M);

        if (num < P) num += M;
        num -= P;

        num *= inv;

        if (num < e + 1) num += M;
        num -= e + 1;
        if (num > M) num %= M;

        num *= inv;
        if (num > M) num %= M;

        res *= num;
        if (res > M) res %= M;
    }

    res.writeln;
}