# 10/7 鄭安庭410703045

#Trapezoidal area

"""
上底加下底乘以高除以二
"""

shortbase=int(input("Please input the short base:"))
longbase=int(input("Please input the long base:"))
height=int(input("Please input the height:"))
area=(shortbase + longbase) * height / 2

print("The trapezoidal area will be: ",area)