def main():
    N = int(input())
    Z = []
    for i in range(N):
        w,s = map(int,input().split())
        Z.append((w,s))
    Z.sort(key = lambda x: x[0] + x[1])
    ans = 0
    weight = 0
    for i in range(N):
        w,s = Z[i]
        if weight <= s:
            ans += 1
            weight += w
    print(ans)
if __name__ == '__main__':
    main()