#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,popcnt,lzcnt,tune=native")
#include <bits/stdc++.h>
namespace fastio
{
static constexpr size_t buf_size = 1 << 18;
static constexpr size_t integer_size = 20;
static constexpr size_t block_size = 10000;
static char inbuf[buf_size + 1] = {};
static char outbuf[buf_size + 1] = {};
static char block_str[block_size * 4 + 1] = {};
static constexpr uint64_t power10[] = {1,
10,
100,
1000,
10000,
100000,
1000000,
10000000,
100000000,
1000000000,
10000000000,
100000000000,
1000000000000,
10000000000000,
100000000000000,
1000000000000000,
10000000000000000,
100000000000000000,
1000000000000000000,
10000000000000000000u};
struct Scanner
{
private:
size_t pos, end;
void load()
{
end = fread(inbuf, 1, buf_size, stdin);
inbuf[end] = '\0';
}
void reload()
{
size_t len = end - pos;
memmove(inbuf, inbuf + pos, len);
end = len + fread(inbuf + len, 1, buf_size - len, stdin);
inbuf[end] = '\0';
pos = 0;
}
void skip_space()
{
while (inbuf[pos] <= ' ')
{
if (__builtin_expect(++pos == end, 0))
reload();
}
}
char get_next()
{
return inbuf[pos++];
}
char get_next_nonspace()
{
skip_space();
return inbuf[pos++];
}
public:
Scanner()
{
load();
}
void scan(char &c)
{
c = get_next_nonspace();
}
void scan(std::string &s)
{
skip_space();
s = "";
do
{
size_t start = pos;
while (inbuf[pos] > ' ')
pos++;
s += std::string(inbuf + start, inbuf + pos);
if (inbuf[pos] != '\0')
break;
reload();
} while (true);
}
template <class T>
typename std::enable_if<std::is_integral<T>::value, void>::type scan(T &x)
{
char c = get_next_nonspace();
if (__builtin_expect(pos + integer_size >= end, 0))
reload();
bool neg = false;
if (c == '-')
neg = true, x = 0;
else
x = c & 15;
while ((c = get_next()) >= '0')
x = x * 10 + (c & 15);
if (neg)
x = -x;
}
template <class Head, class... Others>
void scan(Head &head, Others &...others)
{
scan(head);
scan(others...);
}
template <class T>
Scanner &operator>>(T &x)
{
scan(x);
return *this;
}
};
struct Printer
{
private:
size_t pos = 0;
void flush()
{
fwrite(outbuf, 1, pos, stdout);
pos = 0;
}
void pre_calc()
{
for (size_t i = 0; i < block_size; i++)
{
size_t j = 4, k = i;
while (j--)
{
block_str[i * 4 + j] = k % 10 + '0';
k /= 10;
}
}
}
static constexpr size_t get_integer_size(uint64_t n)
{
if (n >= power10[10])
{
if (n >= power10[19])
return 20;
if (n >= power10[18])
return 19;
if (n >= power10[17])
return 18;
if (n >= power10[16])
return 17;
if (n >= power10[15])
return 16;
if (n >= power10[14])
return 15;
if (n >= power10[13])
return 14;
if (n >= power10[12])
return 13;
if (n >= power10[11])
return 12;
return 11;
}
else
{
if (n >= power10[9])
return 10;
if (n >= power10[8])
return 9;
if (n >= power10[7])
return 8;
if (n >= power10[6])
return 7;
if (n >= power10[5])
return 6;
if (n >= power10[4])
return 5;
if (n >= power10[3])
return 4;
if (n >= power10[2])
return 3;
if (n >= power10[1])
return 2;
return 1;
}
}
public:
Printer()
{
pre_calc();
}
~Printer()
{
flush();
}
void print(char c)
{
outbuf[pos++] = c;
if (__builtin_expect(pos == buf_size, 0))
flush();
}
void print(const char *s)
{
while (*s != 0)
{
outbuf[pos++] = *s++;
// if (pos == buf_size) flush();
if (__builtin_expect(pos == buf_size, 0))
flush();
}
}
void print(const std::string &s)
{
for (auto c : s)
{
outbuf[pos++] = c;
// if (pos == buf_size) flush();
if (__builtin_expect(pos == buf_size, 0))
flush();
}
}
template <class T>
typename std::enable_if<std::is_integral<T>::value, void>::type print(T x)
{
if (__builtin_expect(pos + integer_size >= buf_size, 0))
flush();
if (x < 0)
print('-'), x = -x;
size_t digit = get_integer_size(x);
size_t len = digit;
while (len >= 4)
{
len -= 4;
memcpy(outbuf + pos + len, block_str + (x % block_size) * 4, 4);
x /= block_size;
}
memcpy(outbuf + pos, block_str + x * 4 + (4 - len), len);
pos += digit;
}
template <class Head, class... Others>
void print(const Head &head, const Others &...others)
{
print(head);
print(' ');
print(others...);
}
template <class... Args>
void println(const Args &...args)
{
print(args...);
print('\n');
}
template <class T>
Printer &operator<<(const T &x)
{
print(x);
return *this;
}
};
}; // namespace fastio
fastio::Scanner fin;
fastio::Printer fout;
#include <bits/stdc++.h>
using namespace std;
#ifndef yoshi_likes_e4
#define endl '\n'
#endif
#define problem ""
#define multitest 0
#define debug(x) cerr << #x << " = " << x << endl;
void init()
{
}
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
string A[4100];
bitset<4100> Ab[4][4100];
int C[256];
int cnt[4101];
int c[4][4100];
void Yoshi()
{
C['A'] = 0;
C['T'] = 1;
C['C'] = 2;
C['G'] = 3;
int n, m, k;
fin >> n >> m >> k;
for (int i = 0; i < n; i++)
fin >> A[i];
for (int i = 0; i < n; i++)
for (int j = 0; j < m; j++)
Ab[C[A[i][j]]][i][j] = 1, c[C[A[i][j]]][j]++;
vector<int> cands, ord;
for (int i = 0; i < n; i++)
{
int r = 0;
for (int j = 0; j < m; j++)
r += n - c[C[A[i][j]]][j];
if (r == k * (n - 1))
cands.push_back(i);
ord.push_back(i);
}
shuffle(ord.begin(), ord.end(), rng);
for (auto &i : cands)
{
bool ck = 1;
for (auto &j : ord)
{
if (m - ((Ab[0][j] & Ab[0][i]) | (Ab[1][j] & Ab[1][i]) | (Ab[2][j] & Ab[2][i]) | (Ab[3][j] & Ab[3][i]))
.count() !=
k &&
i != j)
{
ck = 0;
break;
}
}
if (ck)
fout << i + 1 << endl, exit(0);
}
}
signed main()
{
#ifndef yoshi_likes_e4
ios::sync_with_stdio(0);
if (fopen(problem ".inp", "r"))
{
freopen(problem ".inp", "r", stdin);
freopen(problem ".out", "w", stdout);
}
#endif
init();
int t = 1;
#if multitest
fin >> t;
#endif
while (t--)
Yoshi();
}
