#include <stdio.h>
int main()
{
int j, i, arr1[31] = {}, arr2[29] = {};
for (i = 1; i <= 30; i++)
{
arr1[i] = i;
}
for (i = 0; i < 28; i++)
{
scanf_s("%d", &arr2[i]);
arr1[arr2[i]] = 0;
}
for (i = 1; i <= 30; i++)
{
if (arr1[i] != 0)
{
printf("%d\n", i);
}
}
return 0;
}