Reversals

import fileinput
import itertools

if __name__ == '__main__':
    with fileinput.input(['-']) as input:
        n, m = map(int, input.readline().rstrip().split(' '))
        string = list(input.readline().rstrip())
        revs = [tuple(map(int, input.readline().rstrip().split(' '))) for i in range(0, m)]
        revs_ = itertools.groupby(revs)
        for rev, _ in revs_:
            a, b = rev
            string[a-1:b] = list(reversed(string[a-1:b]))
        print(''.join(string))

Test 1

Verdict: ACCEPTED

Test 2

Verdict: TIME LIMIT EXCEEDED