#pragma GCC optimize("O3")
#pragma GCC optimize("O1")
#pragma GCC optimize("O1")
#pragma GCC target("avx2")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("avx")
#pragma GCC optimize(3)
#pragma GCC optimize("Ofast")
#pragma GCC optimize("inline")
#pragma GCC optimize("-fgcse")
#pragma GCC optimize("-fgcse-lm")
#pragma GCC optimize("-fipa-sra")
#pragma GCC optimize("-ftree-pre")
#pragma GCC optimize("-ftree-vrp")
#pragma GCC optimize("-fpeephole2")
#pragma GCC optimize("-ffast-math")
#pragma GCC optimize("-fsched-spec")
#pragma GCC optimize("-falign-jumps")
#pragma GCC optimize("-falign-loops")
#pragma GCC optimize("-falign-labels")
#pragma GCC optimize("-fdevirtualize")
#pragma GCC optimize("-fcaller-saves")
#pragma GCC optimize("-fcrossjumping")
#pragma GCC optimize("-fthread-jumps")
#pragma GCC optimize("-freorder-blocks")
#pragma GCC optimize("-fschedule-insns")
#pragma GCC optimize("inline-functions")
#pragma GCC optimize("-ftree-tail-merge")
#pragma GCC optimize("-fschedule-insns2")
#pragma GCC optimize("-fstrict-aliasing")
#pragma GCC optimize("-falign-functions")
#pragma GCC optimize("-fcse-follow-jumps")
#pragma GCC optimize("-fsched-interblock")
#pragma GCC optimize("-fpartial-inlining")
#pragma GCC optimize("no-stack-protector")
#pragma GCC optimize("-freorder-functions")
#pragma GCC optimize("-findirect-inlining")
#pragma GCC optimize("-fhoist-adjacent-loads")
#pragma GCC optimize("-frerun-cse-after-loop")
#pragma GCC optimize("inline-small-functions")
#pragma GCC optimize("-finline-small-functions")
#pragma GCC optimize("-ftree-switch-conversion")
#pragma GCC optimize("-foptimize-sibling-calls")
#pragma GCC optimize("-fexpensive-optimizations")
#pragma GCC optimize("inline-functions-called-once")
#pragma GCC optimize("-fdelete-null-pointer-checks")
#pragma GCC target("avx,avx2,sse,sse2,sse3,ssse3,sse4,sse4.1,sse4.2,mmx,abm")
#include <bits/stdc++.h>
#define fo(i, d, c) for (int i = d; i <= c; i++)
#define fod(i, c, d) for (int i = c; i >= d; i--)
#define maxn 1000010
#define N 1010
#define fi first
#define se second
#define pb emplace_back
#define en cout << "\n";
#define bitcount(x) __builtin_popcountll(x)
#define pii pair<int, int>
#define vii vector<pii>
#define lb(x) x & -x
#define bit(i, j) ((i >> j) & 1)
#define offbit(i, j) (i ^ (1LL << j))
#define onbit(i, j) (i | (1LL << j))
#define vi vector<int>
#define all(x) x.begin(), x.end()
#define ss(x) (int)x.size()
template <typename T1, typename T2>
bool minimize(T1 &a, T2 b)
{
if (a > b)
{
a = b;
return true;
}
return false;
}
template <typename T1, typename T2>
bool maximize(T1 &a, T2 b)
{
if (a < b)
{
a = b;
return true;
}
return false;
}
using namespace std;
const int nsqrt = 450;
const int mod = 1e9 + 7;
void add(int &x, int k)
{
x += k;
x %= mod;
if(x < 0) x += mod;
}
void del(int &x, int k)
{
x -= k;
x %= mod;
if(x < 0) x += mod;
}
int n,m,k;
bitset<4100> a[16401];
short id[4111];
bool has[4111][4];
main()
{
#define name "TASK"
if (fopen(name ".inp", "r"))
{
freopen(name ".inp", "r", stdin);
freopen(name ".out", "w", stdout);
}
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> m >> k;
bool ff = 1;
fo(i,1,n)
{
fo(j,0,m - 1)
{
char t;
cin >> t;
if(t == 'A') a[(i - 1) * 4][j] = 1,has[i][0] = 1;
if(t == 'T') a[(i - 1) * 4 + 1][j] = 1,has[i][1] = 1;
if(t == 'G') a[(i - 1) * 4 + 2][j] = 1,has[i][2] = 1;
if(t == 'C') a[(i - 1) * 4 + 3][j] = 1,has[i][3] = 1;
if(has[i][0] and has[i][1] and has[i][2] and has[i][3]) ff = 0;
}
}
fo(i,1,n) id[i] = i;
random_shuffle(id + 1,id + n + 1);
fo(i,1,n)
{
// if(i % 5 == 100) random_shuffle(id + 1,id + n + 1);
bool ok = 1;
fo(x,1,n)
{
short j = id[x];
if(i == j) continue;
short cnt = 0;
fo(h,0,3)
{
if(has[i][h] and has[j][h])
cnt += (a[(i - 1) * 4 + h] ^ a[(j - 1) * 4 + h]).count();
else if(has[i][h]) cnt += a[(i - 1) * 4 + h].count();
else if(has[j][h]) cnt += a[(j - 1) * 4 + h].count();
if(cnt > 2 * k) break;
}
if(cnt != 2 * k)
{
ok = 0;
break;
}
}
if(ok) return cout << i,0;
}
}
