from collections import defaultdict
n = int(input())
k = defaultdict(list)
header = list(map(str, input().split()))

listed = []
for x in range(n):
    listed.append(list(input().split()))

for i, j in enumerate(header):
    for x in range(n):
        if (listed[x][i]).isnumeric():
            k[j].append(int(listed[x][i]))
        else:
            k[j].append(listed[x][i])

print(f'{(sum(k.get('MARKS'))/n):.2f}')