Григорьев ЛР / 5 / тп5_1_6

def fibonacci(n: int):
    if n == 1:
        return 0
    elif n == 2:
        return 1
    else:
        return fibonacci(n-1)+fibonacci(n-2)

inp = int(input())

assert fibonacci(1) == 0
assert fibonacci(2) == 1

print(fibonacci(inp))