Go: package main

import "fmt"

func main() {
	var i int
	stack := make([]int, 0)
	for {
		v, _ := fmt.Scan(&i)
		// fmt.Println(stack)
		// println(v)
		if v == 0 {
			break
		}
		if i == 0 {
			fmt.Println(stack[len(stack)-1])
			stack = stack[:len(stack)-1]
			continue
		}
		stack = append(stack, i)
	}
}

C++: // need
#include <iostream>
#include <algorithm>

// data structure
#include <bitset>
//#include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
//#include <array>
//#include <tuple>
//#include <unordered_map>
//#include <unordered_set>
#include <complex>
//#include <deque>
#include<valarray>

// stream
//#include <istream>
//#include <sstream>
//#include <ostream>
#include <fstream>

// etc
#include <cassert>
#include <functional>
#include <iomanip>
//#include <typeinfo>
//#include <chrono>
#include <random>
#include <numeric>

#define INIT std::ios::sync_with_stdio(false);std::cin.tie(0);
#define VAR(type, ...)type __VA_ARGS__;MACRO_VAR_Scan(__VA_ARGS__);
template<typename T> void MACRO_VAR_Scan(T& t) { std::cin >> t; }
template<typename First, typename...Rest>void MACRO_VAR_Scan(First& first, Rest&...rest) { std::cin >> first; MACRO_VAR_Scan(rest...); }
#define VEC_ROW(type, n, ...)std::vector<type> __VA_ARGS__;MACRO_VEC_ROW_Init(n, __VA_ARGS__); for(int i=0; i<n; ++i){MACRO_VEC_ROW_Scan(i, __VA_ARGS__);}
template<typename T> void MACRO_VEC_ROW_Init(int n, T& t) { t.resize(n); }
template<typename First, typename...Rest>void MACRO_VEC_ROW_Init(int n, First& first, Rest&...rest) { first.resize(n); MACRO_VEC_ROW_Init(n, rest...); }
template<typename T> void MACRO_VEC_ROW_Scan(int p, T& t) { std::cin >> t[p]; }
template<typename First, typename...Rest>void MACRO_VEC_ROW_Scan(int p, First& first, Rest&...rest) { std::cin >> first[p]; MACRO_VEC_ROW_Scan(p, rest...); }
#define OUT(d) std::cout<<d;
#define FOUT(n, d) std::cout<<std::fixed<<std::setprecision(n)<<d;
#define SOUT(n, c, d) std::cout<<std::setw(n)<<std::setfill(c)<<d;
#define SP std::cout<<" ";
#define TAB std::cout<<"\t";
#define BR std::cout<<"\n";
#define ENDL std::cout<<std::endl;
#define FLUSH std::cout<<std::flush;
#define VEC(type, c, n) std::vector<type> c(n);for(auto& i:c)std::cin>>i;
#define MAT(type, c, m, n) std::vector<std::vector<type>> c(m, std::vector<type>(n));for(auto& r:c)for(auto& i:r)std::cin>>i;
#define ALL(a) (a).begin(),(a).end()
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define RFOR(i, a, b) for(int i=(b)-1;i>=(a);--i)
#define REP(i, n) for(int i=0;i<int(n);++i)
#define RREP(i, n) for(int i=(n)-1;i>=0;--i)
#define FORLL(i, a, b) for(ll i=ll(a);i<ll(b);++i)
#define RFORLL(i, a, b) for(ll i=ll(b)-1;i>=ll(a);--i)
#define REPLL(i, n) for(ll i=0;i<ll(n);++i)
#define RREPLL(i, n) for(ll i=ll(n)-1;i>=0;--i)
#define PAIR std::pair<int, int>
#define PAIRLL std::pair<ll, ll>
#define IN(a, x, b) (a<=x && x<b)
#define SHOW(d) {std::cerr << #d << "\t:" << d << "\n";}
#define SHOWVECTOR(v) {std::cerr << #v << "\t:";for(const auto& xxx : v){std::cerr << xxx << " ";}std::cerr << "\n";}
#define SHOWVECTOR2(v) {std::cerr << #v << "\t:\n";for(const auto& xxx : v){for(const auto& yyy : xxx){std::cerr << yyy << " ";}std::cerr << "\n";}}
#define SHOWPAIR(p) {std::cerr << #p << "\t:(" << p.first << ",\t" << p.second << ")\n";}
#define SHOWPAIRVECTOR2(v) {std::cerr << #v << "\t:\n";for(const auto& xxx : v){for(const auto& yyy : xxx){std::cerr<<'('<<yyy.first<<", "<<yyy.second<<") ";}std::cerr << "\n";}}
#define SHOWPAIRVECTOR(v) {for(const auto& xxx:v){std::cerr<<'('<<xxx.first<<", "<<xxx.second<<") ";}std::cerr<<"\n";}
#define SHOWQUEUE(a) {auto tmp(a);std::cerr << #a << "\t:";while(!tmp.empty()){std::cerr << tmp.front() << " ";tmp.pop();}std::cerr << "\n";}
template<typename T> inline T CHMAX(T& a, const T b) { return a = (a < b) ? b : a; }
template<typename T> inline T CHMIN(T& a, const T b) { return a = (a > b) ? b : a; }
#define EXCEPTION(msg) throw std::string("Exception : " msg " [ in ") + __func__ + " : " + std::to_string(__LINE__) + " lines ]"
#define TRY(cond, msg) try {if (cond) EXCEPTION(msg);}catch (std::string s) {std::cerr << s << std::endl;}
//void CHECKTIME(std::function<void()> f) { auto start = std::chrono::system_clock::now(); f(); auto end = std::chrono::system_clock::now(); auto res = std::chrono::duration_cast<std::chrono::nanoseconds>((end - start)).count(); std::cerr << "[Time:" << res << "ns  (" << res / (1.0e9) << "s)]\n"; }

#define int ll
using ll = long long;
using ull = unsigned long long;
constexpr int INFINT = 1 << 30;                          // 1.07x10^ 9
constexpr int INFINT_LIM = (1LL << 31) - 1;              // 2.15x10^ 9
constexpr ll INFLL = 1LL << 60;                          // 1.15x10^18
constexpr ll INFLL_LIM = (1LL << 62) - 1 + (1LL << 62);  // 9.22x10^18
constexpr double EPS = 1e-7;
constexpr int MOD = 1000000007;
constexpr double PI = 3.141592653589793238462643383279;

signed main() {
	INIT;
	std::stack<int> st;
	int t;
	while (std::cin >> t) {
		if (t == 0) {
			OUT(st.top())BR; st.pop();
		}
		else {
			st.push(t);
		}
	}
	return 0;
}

C++: #include <stdio.h>
#include <stack>

using namespace std;

int main(){
  stack<int> stk;

  int n;
  while(scanf("%d", &n)!=EOF){
    if(n==0){
      printf("%d\n", stk.top());
      stk.pop();
    }else{
      stk.push(n);
    }
  }
}

C++: #include <bits/stdc++.h>
using namespace std;

#define FOR(i,l,r) for(int i = (l);i < (r);i++)
#define ALL(x) (x).begin(),(x).end()
template<typename T> bool chmax(T& a,const T& b){return a < b ? (a = b,true) : false;}
template<typename T> bool chmin(T& a,const T& b){return b < a ? (a = b,true) : false;}
typedef long long ll;

int main()
{
	int N;
	stack<int> s;
	while(~scanf("%d",&N)){
		if(N){
			s.push(N);
		}
		else{
			printf("%d\n",s.top());
			s.pop();
		}
	}

	return 0;
}

C++: #include <iostream>
#include <stack>

using namespace std;

int main(){
  int n;
  stack<int> train;
    while(cin>>n){
    if(n)train.push(n);
    else{
      cout<<train.top()<<endl;
      train.pop();
    }
    }
  return 0;
}

C++: #include <iostream>

using namespace std;

int main()
{
	int cars[100] ={0};
	int ptr_top = 0;
	int car_num;
	
	while ( cin >> car_num ) {
		if (car_num == 0) {
			cout << cars[ptr_top] << endl;
			ptr_top--;
		}
		else {
			ptr_top++;
			cars[ptr_top] = car_num;
		}
	}
	
	return 0;
}

C++: #include <vector>
#include <cstdio>
using namespace std;
 
int main() {
  int n;
  vector<int> S;
  while (scanf("%d", &n) != EOF) {
    if (n == 0) {
      printf("%d\n", S.back());
      S.pop_back();
    } else {
      S.push_back(n);
    }
  }
}

C++: #include<bits/stdc++.h>
using namespace std;
int main()
{
    int train[10],moving,situation=0,ans[10],n=0,ende=0;
    while(cin>>moving){
        if(moving!=0){
            train[situation]=moving;
            situation++;
        }
        else {
                situation--;
                ans[ende]=train[situation];
                ende++;
        }
    }
    for(int i=0;i<ende;i++)cout<<ans[i]<<endl;

}

C++: #include <iostream>
#include <sstream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <ctime>
#include <cstring>
#include <climits>
#include <algorithm>
#include <map>
#include <set>
#include <stack>
#include <vector>
#include <queue>
#include <string>
#include <complex>
using namespace std;

#define rep(i,n) for(int i=0; i<n; i++)
#define repa(i,s,e) for(int i=s; i<=e; i++)
#define repd(i,s,e) for(int i=s; i>=e; i--)

typedef vector<int> vi;

int main() {
	stack<int> S;
	int n;

	while(scanf("%d", &n)!=EOF) {
		if(n>0) S.push(n);
		else {
			printf("%d\n", S.top());
			S.pop();
		}
	}
}

C++: #include <iostream>
#include <vector>
#include <cstdint>

int main()
{
	std::vector<std::uint16_t> cars;
	std::uint16_t num;
	while (std::cin >> num) {
		if (num == 0) {
			std::cout << cars.back() << std::endl;
			cars.pop_back();
		}
		else {
			cars.push_back(num);
		}
	}
	return 0;
}