# Arup Guha
# 1/23/2020
# Solution to COP 2930 Pair Program #1A: Biking

# Different speeds.
SPEED1 = 28
SPEED2 = 20
SPEED3 = 14
SPEED4 = 10

# Get the # of minutes biking.
minutes = int(input("How many minutes are you biking?\n"))

# Set this initially.
dist = 0

# We go 28 mph.
if minutes <= 30:
    dist = SPEED1*minutes/60

# Go 28 mph for 30 minutes and 20 mph for the rest.
elif minutes <= 60:
    dist = SPEED1*.5 + SPEED2*(minutes-30)/60

# Go 28 mph for 30 min, 20 mph for 30 min, 14 mph for the rest.
elif minutes <= 90:
    dist = SPEED1*.5 + SPEED2*.5 + SPEED3*(minutes-60)/60

# Go 28 mph for 30 min, 20 mph for 30 min, 14 mph for 30 min, 10 mph for rest.
else:
    dist = SPEED1*.5 + SPEED2*.5 + SPEED3*.5 + SPEED4*(minutes-90)/60

# Ta da!
print("You will bike a distance of",dist,"miles.")