import csv 
from collections import Counter
with open ('height-weight.csv',newline='') as f :
    reader=csv.reader(f)
    file_data = list(reader)

file_data.pop(0)

new_data=[]
for i in range(len(file_data)) :
    n_num=file_data[i][1]
    new_data.append(n_num)

data=Counter(new_data)
md={
    "50-60":0,
    "60-70":0,
    "70-80":0,
}
for height , occurence in data.items():
    if 50<float(height)<60 :
        md["50-60"]+=occurence
    elif 60<float(height)<70 :
        md["60-70"]+=occurence
    else:
        md["70-80"]+=occurence
mode_range,mode_occurence=0,0

for range,occurence in md.items():
    if occurence>mode_occurence:
        mode_range,mode_occurence=[int(range.split("-")[0]), int(range.split("-")[1])], occurence

mode=float((mode_range[0]+mode_range[1])/2)
print(f"{mode:2f}")