题解 | #汽水瓶#

#include <stdio.h>

int main() {
    int n;
    while (scanf("%d", &n) != EOF) {
        if(n == 0) return 0;
        int numofsoda = 0;
        while (n >= 3) {
            numofsoda += n/3;
            n = n/3 + n%3;
        } 
        if(n == 2) {
            numofsoda++;
        }
        printf("%d\n", numofsoda);
    }
    return 0;
}