mod = 1000000007
eps = 10**-9


def main():
    import sys
    from bisect import bisect_left
    input = sys.stdin.readline

    N = int(input())
    WS = []
    for _ in range(N):
        WS.append(tuple(map(int, input().split())))
    WS.sort(key=lambda x: x[0] + x[1])

    LIS = [0]
    for w, s in WS:
        j = bisect_left(LIS, s+1)
        if j == len(LIS):
            LIS.append(LIS[-1] + w)
        else:
            LIS[j] = min(LIS[j], LIS[j-1] + w)
    print(len(LIS) - 1)


if __name__ == '__main__':
    main()