Python 3.7.3

n = int(input())

if n < 100 or n > 999:

   print('FALSE')

   exit(0)

a = n

sum = 0

while a > 0:

   sum += (a % 10)

   a //= 10

if sum == 13:

   print('ENTER')

else:

   print('LOCK')

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C++

#include <iostream>

using namespace std;

int main() {

int x;

cin >> x;

if(x < 100 || x > 999) cout << "FALSE" , exit(0);

int j = x, sum = 0;

while(j) {

sum += (j % 10);

j /= 10;

}

if(sum == 13) cout << "ENTER"; else cout << "LOCK";

return 0;

}