Editorial

The formula of the binomial theorem is as follows:

(a + b)^{n} = i = 0 \sum n C_{n}^{i} a^{i} b^{n - i}

If we set $a = b = 1$ , then this relation takes the following form:

(1 + 1)^{n} = i = 0 \sum n C_{n}^{i} 1^{i} 1^{n - i}

2^{n} = i = 0 \sum n C_{n}^{i} = C_{n}^{0} + C_{n}^{1} + ... + C_{n}^{n}

Thus, the indicated sum equals $2^{n}$ .

Example

If $n = 1$ , then $C_{1}^{0} + C_{1}^{1} = 1 + 1 = 2$

If $n = 2$ , then $C_{2}^{0} + C_{2}^{1} + C_{2}^{2} = 1 + 2 + 1 = 4$

If $n = 3$ , then $C_{3}^{0} + C_{3}^{1} + C_{3}^{2} + C_{3}^{3} = 1 + 3 + 3 + 1 = 8$

Algorithm realization

Read the input value of $n$ .

scanf("%lld", &n);

Compute and print the result, the value of $2^{n}$ .

res = 1LL << n;
printf("%lld\n", res);

Python realization

Read the input value of $n$ .

n = int(input())

Compute and print the result, the value of $2^{n}$ .

res = 1 << n
print(res)