#include <bits/stdc++.h>

#define ll long long

#define INF 2147483647

#define y1 uihaoissa

#define y2 oaioiuwio

using namespace std;

const int wx[]= {,,,-},wy[]= {,,-,};

int T,n,m,k,maxh,ltt;

int a[][],sum[][],cal[];

char tow[][][];

bool f[][][];

int cnt[][][];

short pre1[][][],pre2[][][],fl[][][];

bool debug;

inline int read() {

    int x=;

    char ch=getchar();

    while(ch<''||ch>'')ch=getchar();

    while(ch>=''&&ch<='') {

        x=x*+ch-'';

        ch=getchar();

    }

    return x;

}

inline int sqr(int x) {

    return x*x;

}

inline int toedge(int x,int y) {

    return min(min(x,y),min(n-x+,m-y+));

}

inline int islarge1(int x1,int y1,int y2,int z) {

    return pre1[x1][y2][z]-pre1[x1][y1-][z];

}

inline int islarge2(int x1,int x2,int y1,int z) {

    return pre2[x2][y1][z]-pre2[x1-][y1][z];

}

inline int getsum(int x1,int y1,int x2,int y2) {

    return sum[x2][y2]-sum[x1-][y2]-sum[x2][y1-]+sum[x1-][y1-];

}

int check(int x,int y,int z) {

    if (x>) {

        int h;

        if (cnt[x-][y][z]==-)

            switch (tow[x-][y][z]) {

                case :

                    if (fl[x-][y][z]!=z-) {

                        h=fl[x-][y][z]+;

                        if (islarge1(x-h,y-h,y+h,z-h)>) return fl[x][y][z]=h,tow[x][y][z]=,cnt[x][y][z]=-,;

                    }

                    break;

                case :

                    h=fl[x-][y][z];

                    if (islarge2(x-h,x+h,y-h,z-h)>) return fl[x][y][z]=h,tow[x][y][z]=,cnt[x][y][z]=-,;

                    break;

                case :

                    h=fl[x-][y][z];

                    if (islarge2(x-h,x+h,y+h,z-h)>) return fl[x][y][z]=h,tow[x][y][z]=,cnt[x][y][z]=-,;

                    break;

                case :

                    h=fl[x-][y][z]-;

                    if (islarge1(x+h,y-h,y+h,z-h)>) return fl[x][y][z]=h,tow[x][y][z]=,cnt[x][y][z]=-,;

                    break;

            }

    }

    if (y>) {

        int h;

        if (cnt[x][y-][z]==-) {

            if (fl[x][y][z]==) tow[x][y][z]=;

            switch (tow[x][y-][z]) {

                case :

                    h=fl[x][y-][z];

                    if (islarge1(x-h,y-h,y+h,z-h)>) return fl[x][y][z]=h,tow[x][y][z]=,cnt[x][y][z]=-,;

                    break;

                case :

                    if (fl[x][y-][z]!=z-) {

                        h=fl[x][y-][z]+;

                        if (islarge2(x-h,x+h,y-h,z-h)>) return fl[x][y][z]=h,tow[x][y][z]=,cnt[x][y][z]=-,;

                    }

                    break;

                case :

                    h=fl[x][y-][z]-;

                    if (islarge2(x-h,x+h,y+h,z-h)>) return fl[x][y][z]=h,tow[x][y][z]=,cnt[x][y][z]=-,;

                    break;

                case :

                    h=fl[x][y-][z];

                    if (islarge1(x+h,y-h,y+h,z-h)>) return fl[x][y][z]=h,tow[x][y][z]=,cnt[x][y][z]=-,;

                    break;

            }

        }

    }

    if (z>) {

        if (cnt[x][y][z-]==-) {

            int h=fl[x][y][z-];

            switch (tow[x][y][z-]) {

                case :

                    if (islarge1(x-h,y-h,y+h,z-h)>) return fl[x][y][z]=h,tow[x][y][z]=,cnt[x][y][z]=-,;

                    break;

                case :

                    if (islarge2(x-h,x+h,y-h,z-h)>) return fl[x][y][z]=h,tow[x][y][z]=,cnt[x][y][z]=-,;

                    break;

                case :

                    if (islarge2(x-h,x+h,y+h,z-h)>) return fl[x][y][z]=h,tow[x][y][z]=,cnt[x][y][z]=-,;

                    break;

                case :

                    if (islarge1(x+h,y-h,y+h,z-h)>) return fl[x][y][z]=h,tow[x][y][z]=,cnt[x][y][z]=-,;

                    break;

            }

        }

    }

    for (int h=z-; h>=; h--) { //h为中心到该圈的差数

        if (cnt[x][y][h+]!=-) break;

        if (islarge1(x-h,y-h,y+h,z-h)>) return fl[x][y][z]=h,tow[x][y][z]=,cnt[x][y][z]=-,;

        if (islarge2(x-h,x+h,y-h,z-h)>) return fl[x][y][z]=h,tow[x][y][z]=,cnt[x][y][z]=-,;

        if (islarge2(x-h,x+h,y+h,z-h)>) return fl[x][y][z]=h,tow[x][y][z]=,cnt[x][y][z]=-,;

        if (islarge1(x+h,y-h,y+h,z-h)>) return fl[x][y][z]=h,tow[x][y][z]=,cnt[x][y][z]=-,;

    }

    int tot=cal[z]-getsum(x-z+,y-z+,x+z-,y+z-);

    return tot>k?:(cnt[x][y][z]=tot,);

}

int main() {

    for (int i=; i<=; i++)

        cal[i]=cal[i-]+(*i-)*(*i-);

    T=read();

    while (T--) {

        maxh=;

        memset(cnt,-,sizeof(cnt));

        n=read(),m=read(),k=read();

        for (int i=; i<=n; i++)

            for (int j=; j<=m; j++) {

                a[i][j]=read();

                sum[i][j]=sum[i-][j]+sum[i][j-]-sum[i-][j-]+a[i][j];

                for (int k=,to=toedge(i,j); k<=to; k++) {

                    f[i][j][k]=(a[i][j]>k);

                    pre1[i][j][k]=pre1[i][j-][k]+f[i][j][k];

                    pre2[i][j][k]=pre2[i-][j][k]+f[i][j][k];

                }

            }

        for (int i=; i<=n; i++)

            for (int j=; j<=m; j++) {

                cnt[i][j][]=-a[i][j];

                if (a[i][j]<=) maxh=max(maxh,);

                for (int l=max(max(a[i][j],),maxh+),to=toedge(i,j); l<=to;) {

                    int tmp=check(i,j,l);

                    if (!tmp) maxh=max(maxh,l),tmp++;

                    l+=tmp;

                }

            }

        printf("%d\n",maxh);

    }

    return ;

}