#!/usr/bin/python3

# main
n = int(input()) - 1
fib = [1, 2]
for i in range(2, n + 1):
    fib.append(fib[i - 1] + fib[i - 2])
print(fib[n]) n = int(input()) - 1 n int(input()) - 1 int(input()) int input() input 1 fib = [1, 2] fib [1, 2] 1 2 for i in range(2, n + 1):
    fib.append(fib[i - 1] + fib[i - 2]) i range(2, n + 1) range 2 n + 1 n 1 fib.append(fib[i - 1] + fib[i - 2]) fib.append fib append fib[i - 1] + fib[i - 2] fib[i - 1] fib i - 1 i 1 fib[i - 2] fib i - 2 i 2 print(fib[n]) print fib[n] fib n n = int(input()) - 1 int(input()) - 1 n fib = [1, 2] [1, 2] fib
#!/usr/bin/python3

# main
n = int(input()) - 1
fib = [1, 2]
for i in range(2, n + 1):
    fib.append(fib[i - 1] + fib[i - 2])
print(fib[n])