#include<bits/stdc++.h>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
//using namespace __gnu_pbds;
using namespace std;
typedef long double ld;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef vector<pl> vpl;
typedef vector<ld> vld;
typedef pair<ld, ld> pld;
//typedef tree<ll, null_type, less_equal<ll>,rb_tree_tag,tree_order_statistics_node_update> ordered_set;
template<typename T>
ostream &operator<<(ostream &os, vector<T> &a) {
os << "[";
for (int i = 0; i < ll(a.size()); i++) { os << a[i] << ((i != ll(a.size() - 1) ? " " : "")); }
os << "]\n";
return os;
}
#define all(x) x.begin(),x.end()
#define YES out("YES")
#define NO out("NO")
#define out(x){cout << x << "\n"; return;}
#define GLHF ios_base::sync_with_stdio(false); cin.tie(NULL)
#define print(x){for(auto ait:x) cout << ait << " "; cout << "\n";}
#define pb push_back
#define umap unordered_map
template<typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) {
is >> p.first >> p.second;
return is;
}
template<typename T1, typename T2>
ostream &operator<<(ostream &os, pair<T1, T2> &p) {
os << "" << p.first << " " << p.second << "";
return os;
}
void usaco(string taskname) {
string fin = taskname + ".in";
string fout = taskname + ".out";
const char *FIN = fin.c_str();
const char *FOUT = fout.c_str();
freopen(FIN, "r", stdin);
freopen(FOUT, "w", stdout);
}
template<typename T>
void read(vector<T> &v) {
int n = v.size();
for (int i = 0; i < n; i++)
cin >> v[i];
}
template<typename T>
vector<T> UNQ(vector<T> a) {
vector<T> ans;
for (T t:a)
if (ans.empty() || t != ans.back())
ans.push_back(t);
return ans;
}
ll ceil(ll a, ll b) {
ll ans = a / b;
if (a % b)ans++;
return ans;
}
ld log(ld a, ld b) { return log(b) / log(a); }
ll power(ll base, ll exp, ll M = 1e18) {//(base^exp)%M
ll ans = 1;
while (exp) {
if (exp % 2 == 1)ans = ((ans % M) * (base % M)) % M;
base = ((base % M) * (base % M)) % M;
exp /= 2;
}
return ans;
}
string to_base(int n, int new_base) {
string s;
int nn = n;
while (nn) {
s += to_string(nn % new_base);
nn /= new_base;
}
reverse(all(s));
return s;
}
ll gcd(ll a, ll b) {
if (a < b)swap(a, b);
if (b == 0)return a;
return gcd(b, a % b);
}
ll lcm(ll a, ll b) {
ll x = (a / gcd(a, b));
return b * x;
}
vl generate_array(ll n, ll mn = 1, ll mx = 1e18 + 1) {
if (mx == 1e18 + 1)
mx = n;
vl ans(n);
for (int i = 0; i < n; i++)
ans[i] = (mn + rand() % (mx - mn + 1));
return ans;
}
string substr(string s, int l, int r) {
string ans;
for (int i = l; i <= r; i++)
ans += s[i];
return ans;
}
void solve();
int main() {
GLHF;
int t = 1;
//cin >> t;
while (t--)
solve();
}
const int maxn=4101;
void s1(int n,int m,int k,vvi a){
int cnt[m][4];//cnt[i][j]=how many have j in index i
for(int i=0; i<m; i++)
for(int j=0; j<4; j++)
cnt[i][j]=0;
string AB="ACGT";
for(int i=0; i<n; i++){
for(int j=0; j<m; j++)
for(int c=0; c<4; c++)
if(a[i][j]==c)
cnt[j][c]++;
}
bitset<maxn>b[4][n];
for(int c=0; c<4; c++)
for(int i=0; i<n; i++)
for(int j=0; j<m; j++)
b[c][i][j]=(a[i][j]==c);
for(int i=0; i<n; i++){
ll sum=0;
for(int j=0; j<m; j++){
for(int c=0; c<4; c++)
if(c!=a[i][j])
sum+=cnt[j][c];
}
if(sum!=k*(n-1))
continue;
bool ok=1;
for(int j=0;ok && j<n; j++) {
if(i==j)continue;
ll cur=0;
for(int c=0; c<4; c++)
cur+=(b[c][i]^b[c][j]).count();
if(cur!=2*k)
ok=0;
}
if(ok)out(i+1)
}
}
void s2(int n,int m,int k,vector<string>a){
vector<map<ll,ll>>cnt(m);//cnt[i][j]=how many have j in index i
string AB="ACGT";
for(int i=0; i<n; i++){
for(int j=0; j<m; j++)
for(char c:AB)
if(a[i][j]==c)
cnt[j][c]++;
}
vector<bitset<maxn>>b(n);
for(int i=0; i<n; i++)
for(int j=0; j<m; j++)
b[i][j]=(a[i][j]=='A');
for(int i=0; i<n; i++){
ll sum=0;
for(int j=0; j<m; j++){
for(char c:AB)
if(c!=a[i][j])
sum+=cnt[j][c];
}
if(sum!=k*(n-1))
continue;
bool ok=1;
for(int j=0; j<n; j++)
if(i!=j && (b[i]^b[j]).count()!=k){
ok=0;
break;
}
if(ok)out(i+1)
}
}
void solve() {
int n,m,k;
cin >> n >> m >> k;
const int maxn=4101;
vector<string>a(n);
read(a);
bool AC=1;
for(int i=0; i<n; i++)
for(int j=0; j<m; j++)
AC&=(a[i][j]=='A' || a[i][j]=='C');
if(AC) { s2(n, m, k, a);return; }
vvi A(n,vi(m));
for(int i=0; i<n; i++)
for(int j=0; j<m; j++){
if(a[i][j]=='A')
A[i][j]=1;
else if(a[i][j]=='C')
A[i][j]=2;
else if(a[i][j]=='T')
A[i][j]=3;
}
s1(n,m,k,A);
}
