CUTOFF = 1000
FIRST = 0
SECOND = 1


def start():
    current = int(input("Fibonacci number to calculate (%d or less): " %(CUTOFF)))
    if(current <= CUTOFF):
        if(current == FIRST):
            print(FIRST)
        elif(current == SECOND):
            print(SECOND)
        else:
            fib = 0
            a = 1
            i = 0
            while(i<current):
                temp = fib
                fib = fib + a
                a = temp
                i = i + 1
            """    
            for(int i=0; i<n; i++) {
            int temp = fib;
            fib = fib + a;
            a = temp;
            """

            """
            i = 2
            twoBefore = FIRST
            oneBefore = SECOND
            while(i <= current):
                fib =  oneBefore + twoBefore
                twoBefore = oneBefore
                oneBefore = i - 1
                i = i + 1
            """
            print(fib)
            
    else:
        print("You entered %d, maximum factorial is %d" %(current,CUTOFF))
        
start()