#include <stdio.h>

#define ss 15
#define sc 41
#define sr (ss * sc)
#define sf (1 << ss)
#define nf ((1 << ns) - 1)

int tc, ns, at[sc][sc];

char as[ss][sc];

struct cp {
    int l, x;
} cp[ss][ss];

struct dp {
    int l, t;
} dp[sf][ss];

struct q {
    int b[ss], r;
} q;

void read() {
    scanf("%d", &ns);

    for (int i = 0; i < ns; i++)
        scanf("%s", as[i]);
}

void cmp(int y, int x) {
    if (y == x)
        return;

    int i, j, k;

    for (i = 0; as[y][i]; i++) {
        for (j = 0; as[x][j]; j++) {
            at[i][j] = as[y][i] == as[x][j];

            if (i && j)
                at[i][j] += at[i-1][j-1];
        }
    }

    cp[y][x].l = 0;
    cp[y][x].x = -1;

    cp[y][y].l = i;
    cp[x][x].l = j;

    for (k = j-1; k >= 0; k--) {
        if (k == at[i-1][k] - 1) {
            cp[y][x].l = at[i-1][k];
            cp[y][x].x = k;

            break;
        }
    }

    for (k = i-1; k >= 0; k--) {
        if (j == at[k][j-1]) {
            cp[y][x].l = j;
            cp[y][x].x = j;

            break;
        }
    }
}

void cmp() {
    for (int y = 0; y < ns; y++)
        for (int x = 0; x < ns; x++)
            cmp(y, x);
}

int slv() {
    for (int i = 0; i < ns; i++)
        dp[0][i].l = sr;

    for (int f = 1, l, b, t; f <= nf; f++) {
        for (int x = 0; x < ns; x++) {
            if (!(f & (1 << x)))
                continue;

            dp[f][x].t = -1;

            if (b = (f - (1 << x))) {
                dp[f][x].l = sr;
            } else {
                dp[f][x].l = cp[x][x].l;

                continue;
            }

            for (int y = 0; y < ns; y++) {
                if (!(b & (1 << y)))
                    continue;

                t = cp[y][y].l == cp[dp[b][y].t][y].l ? dp[b][y].t : y;

                l = dp[b][y].l + cp[x][x].l - cp[t][x].l;

                if (dp[f][x].l > l) {
                    dp[f][x].l = l;
                    dp[f][x].t = y;
                }

                if (dp[f][x].t == -1)
                    dp[f][x].t = y;
            }
        }
    }

    int m = 0;

    for (int i = 1; i < ns; i++)
        if (dp[nf][m].l > dp[nf][i].l)
            m = i;

    return m;
}

void trk(int i) {
    q.r = -1;

    for (int f = nf, t; i != -1; i = t) {
        q.b[++q.r] = i;

        t = dp[f][i].t;

        f -= (1 << i);
    }

    printf("%s", as[q.b[i = q.r]]);

    for (int y, x = 0, j, c = 1; --i >= 0;) {
        if (c)
            y = q.b[i+1];

        x = q.b[i];

        if (c = (cp[y][x].x != cp[y][x].l)) {
            j = cp[y][x].x + 1;

            printf("%s", &as[x][j]);
        }
    }

    printf("\n");
}

int main() {
    for (scanf("%d", &tc); tc--;) {
        read();

        cmp();

        trk(slv());
    }

    return 0;
}