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def Prime_list(n):
list = []
flag = [1]*(n+2)
p = 2
while p <= n:
list.append(p)
for i in range(2 * p, n + 1, p):
flag[i] = 0
while 1:
p += 1
if flag[p] == 1:
break
return list
if __name__ == "__main__":
N = int(input())
list = Prime_list(N)
count = 0
for i in list[:-1]:
if list[list.index(i)+1] - i == 2:
count += 1
print(count)
while p <= n:
list.append(p)
for i in range(2 * p, n + 1, p):
flag[i] = 0
while 1:
p += 1
if flag[p] == 1:
break