Language: C

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <map>
#include <string>
#include <iostream>

#define MAXN 1000000
#define MAXM 2000000
#define inf 2147483647

using namespace std;

map <int, int> mp;
map <int, int> mp2;

struct edge
{
    int to, c, next;
} e[MAXM];

int vert[MAXN], l, N, top;
char str[30];

int getid(int val)
{
    if (mp.find(val)==mp.end())
    {
        mp[val] = ++N;
        mp2[N] = val;
    }
    else return mp[val];
}

void addedge(int u, int v, int c)
{
    e[++top].to = v, e[top].c = c;
    e[top].next = vert[u], vert[u] = top;
    e[++top].to = u, e[top].c = 0;
    e[top].next = vert[v], vert[v] = top;
}

void dfs1(int u, int pos, int tot, int dep, int val)
{
    if (tot == dep)
    {
        int v = getid(val);
        addedge(u, v, 1);
        return;
    }
    for (int i = pos+1; i < l; ++i)
        dfs1(u, i, tot+1, dep, val*27+str[i]-'A'+1);
}

void gen(int u)
{
    for (int i = 1; i <= 4; ++i)
        dfs1(u, -1, 0, i, 0);
}

int L[MAXN], now[MAXN], q[MAXN];

bool find_path(int src, int des)
{
    for (int i = 0; i <= N; ++i)
        L[i] = inf, now[i] = -1;
    L[q[0] = src] = 0;
    for (int h = 0, t = 1; h != t; h = (h + 1) % MAXN)
    {
        int u = q[h];
        if (L[u] >= L[des]) break;
        for (int i = vert[u]; i != -1; i = e[i].next)
            if (e[i].c > 0)
            {
                if (now[u] == -1) now[u] = i;
                if (L[e[i].to] == inf)
                {
                    L[e[i].to] = L[u] + 1;
                    q[t] = u, t = (t + 1) % MAXN;
                }
            }
    }
    return L[des] != inf;
}

int dfs(int src, int des, int now_flow)
{
    if (src == des) return now_flow;
    int flow = 0, t;
    for (t = now[src]; t != -1; t =e[t].next)
        if (e[t].c > 0 && L[e[t].to] == L[src] + 1)
        {
            int tmp = dfs(e[t].to, des, min(e[t].c, now_flow-flow));
            e[t].c -= tmp;
            e[t^1].c += tmp;
            flow += tmp;
            if (flow == now_flow) break;
        }
    if ((now[src]=t) == -1) L[src] = inf;
    return flow;
}

int maxflow(int src, int des)
{
    int ret = 0;
    while (find_path(src, des)) ret += dfs(src, des, inf);
    return ret;
}

void out(int id)
{
    int x = mp2[id], len = -1;
    char s[5];
    for (;x;x/=27)
        if (x%27) s[++len] = 'a' + x % 27;
    for (int i=len; i>=0; --i)
        printf("%c", s[i]);
    puts("");
}

void init()
{
    int n;
    while (~scanf("%d", &n))
    {
        mp.clear();
        mp2.clear();
        N = n;
        top = -1;
        for (int i = 1; i <= n; ++i)
        {
            addedge(0, i, 1);
            scanf("%s", str);
            l = strlen(str);
            gen(i);
        }
        ++N;
        for (int i=n+1; i<N; ++i)
            addedge(i, N, 1);
        int flow = maxflow(0, N);
        if (flow == n)
        {
            for (int i = n+1; i < N; ++i)
                if (e[vert[i]].c == 0) out(i);
        }
        else puts("-1");
    }
}

int main()
{
    //freopen("input.txt", "r", stdin);
    //freopen("output.txt", "w", stdout);
    init();
    return 0;
}

Compiler output:
main.c:1:10: fatal error: cstdio: No such file or directory
    1 | #include <cstdio>
      |          ^~~~~~~~
compilation terminated.