"""
Ch 6 Q10
[1,1,2,3,5,8,13,21,34,55......] is an infinite series. Each item, except
the first two , takes value the sum of the previous two numbers. What is nth
term's value?

"""


n = int(input("Give me the n: "))
output = [1,1]    

for i in range(2,n):
    output.append(output[i-1]+output[i-2])

print(output[n-1])