include <stdio.h>

include <string.h>

int CalDrinkCount(int n)
{
int a1=0,a2=0,a3=0;
a1 = n/3;
a2 = n%3;
a3 = a1+a2;
if(1 == a1 && 0 == a2)
{
return a1; //最后一次喝,无空瓶;
}
else if(1 == a1 && 1 == a2)
{
a3++; //倒数第二次喝,需要借水;
}
else if(0 == a1 && 2 == a2)
{
return 1; //第一次喝水,需要借助;准备最后一次喝水,需要借水;
}
else if(0 == a1 && 1 == a2)
{
return 0; //第一次,无法喝水;最后一次水喝完,结束条件;
}
return a1+CalDrinkCount(a3);
}

int main(void)
{
int i,n,count = 0;
int array[10] = {0};
while(scanf("%d", &n) != EOF)
{
if(0 == n || 10 == count)
{
break;
}
array[count] = n;
count++;
}
for(i=0; i<10; i++)
{
if(0 != array[i])
{
printf("%d\n",CalDrinkCount(array[i]));
}
}
return 0;
}