while True:
try:
n = int(input())
times = 2
for i in range(2,n+1):
flag = 0
temp1 = i
temp2 = i**2
while True:
if(temp1 % 10 == temp2 % 10):
temp1 = temp1 // 10
temp2 = temp2 // 10
flag = 1
else:
flag = 0
break
if(temp1 == 0 or temp2 == 0):
break
if(flag == 1):
times += 1
print(times)
except:
break 


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