from heapq import *
def main():
    n, y, z = list(map(int, input().split()))
    Q = [list(map(int, input().split())) for _ in range(n)] + [[-1, z, -1]]
    Q.sort(key = lambda x: -x[1])
    hq = []
    ans = 0
    while 1:
        while Q[-1][1] <= y:
            c, l, x = Q.pop()
            if c == -1:
                return ans
            heappush(hq, (-x, c))
        if hq:
             x, c = heappop(hq)
             x = -x
             nc = (Q[-1][1] - y + x - 1) // x
             mc = min(c, nc)
             c -= mc
             y += mc * x
             ans += mc
             if c:
                 heappush(hq, (-x, c))
        else:
            break
    return -1

print(main())