Python 3 code

n = int(input())
inp = (map(int, input().split()) for i in range(n))
p = sorted(list((a + b, a - b) for a, b in inp))
a = list(y for x, y in p)
d = []
for x in a:
    low, high = -1, len(d) # >, <=
    while high - low > 1:
        mid = (low + high) >> 1
        if d[mid] > x:
            low = mid
        else:
            high = mid
    if high == len(d):
        d.append(x)
    else:
        d[high] = x
print(len(d))

does an increase in the frequency by 1 for example means it's gonna take time of the same amount(1) to be adjusted? i mean if does an increase in frequency by 1 requires 1 unit of time ??

I have an algorithm what gives less than expected output, for example for case 4, it gives 15. And could not find a cause. All missiles are hit and enough spare time to change frequency. Have I missed something obvious?

I'm feeling quite dumb, but can we assume for this problem that we have visibility into the whole scenario? Meaning: we know when each missile will arrive from the beginning, and can optimize our missile switching accordingly? The Minimum Path Coverage of the DAG would indicate that...but the nature of the word problem would seem to not allow future knowledge.

In the question does \|fB - fA\| mean abs(fB - fA)