import math
import sys
import heapq
from typing import List, Tuple

int1 = lambda x: int(x) - 1
input = lambda: sys.stdin.readline().rstrip('\n')
ii = lambda: int(input())
vi = lambda: list(map(int, input().split()))
vi1 = lambda: list(map(int1, input().split()))


def dbg(*args, **kwargs):
    print(*(repr(arg) for arg in args), *(f'{k}: {repr(v)}' for k, v in kwargs.items()),
          sep='; ', file=sys.stderr, flush=True)


def solve(x):
    z = 10 ** len(x)
    return z // math.gcd(z, int(x))


def main():
    n, y, z = vi()
    clx = []
    for _ in range(n):
        clx.append(tuple(vi()))
    clx.sort(key=lambda x: x[1], reverse=True)
    q = []
    while clx and clx[-1][1] <= y:
        c, _, x = clx.pop()
        heapq.heappush(q, (-x, c))

    ans = 0
    while y < z and q:
        # print(y, z, q)
        mx, c = heapq.heappop(q)
        x = -mx

        nl = z
        if clx:
            nl = min(nl, clx[-1][1])

        tu = -(-(nl - y) // x)
        zz = min(tu, c)
        ans += zz
        c -= zz
        y += zz * x
        if c != 0:
            heapq.heappush(q, (-x, c))

        while clx and clx[-1][1] <= y:
            c, _, x = clx.pop()
            heapq.heappush(q, (-x, c))

    if y >= z:
        return ans
    else:
        return -1


def _start():
    if (ret := main()) is not None:
        print(*ret) if isinstance(ret, List) or isinstance(ret, Tuple) else print(ret)


if __name__ == '__main__':
    _start()