Дайте советы по улучшению кода

lines = []
resStr = ""
 
with open("input.txt") as fr:
    firstLine = True
    for line in fr:
        if firstLine:
            firstLine = False
        else:
            lines.append(line.strip("\n"))
fr.close()
 
for line in lines:
    chrs = ""
    r = 0
 
    for chr in line:
        if chrs.find(chr) == -1:
            chrs = chrs + chr
    sumArr = [0 for k in range(len(chrs))]
    for chrInd in range(len(chrs)):
        for chr in line:
            if chr == chrs[chrInd]:
                sumArr[chrInd] = sumArr[chrInd] + 1
                
    sumArr.sort()
    sumArr.reverse()
    
    for k in range(sumArr.count(sumArr[0]), len(sumArr)): sumArr.pop(k)
    resStr = resStr + str(sum(sumArr)) + "\n"
    
with open("output.txt", "w") as fw:
    fw.write(resStr.strip("\n"))
    
fw.close()

lines = [i.strip() for i in open('file.txt').readlines()[1:]]

sum([a for a in sumArr if a == max(sumArr)])

lines = []
resStr = ""
 
lines = [k.strip() for k in open("input.txt").readlines()[1:]]
 
for line in lines:
    dict = list(set(line))
    
    sumArr = [0 for k in range(len(dict))]
    
    for chrInd in range(len(dict)):
        for chr in line:
            if chr == dict[chrInd]:
                sumArr[chrInd] = sumArr[chrInd] + 1
                
    resStr = resStr + str(sum([a for a in sumArr if a == max(sumArr)])) + "\n"
    
with open("output.txt", "w") as fw:
    fw.write(resStr.strip("\n"))

m = max(sumArr)
sum(a for a in sumArr if a == m)

from collections import Counter
 
 
lines = [i.strip() for i in open('input.txt').readlines()[1:]]
 
mcs = [Counter(line).values() for line in lines]
res = '\n'.join(str(sum(i for i in mc if i == mcm)) for mc, mcm in zip(mcs, map(max, mcs)))
 
with open("output.txt", "w") as fw:
    fw.write(res)