#include<bits/stdc++.h>
using namespace std;
#define REP(i,a,b) for(int i = (a); i<=(b); ++i)
#define REPD(i,a,b) for(int i = (a); i>=(b); --i)
#define REPDIS(i,a,b,c) for(int i = (a); i<=(b); i += c)
#define ALL(x) (x).begin(),(x).end()
#define SZ(x) (int)(x).size()
#define MASK(x) (1LL<<(x))
#define BIT(x,i) (((x)>>(i))&1LL)
#define vi vector<int>
#define vvi vector<vi>
#define vvvi vector<vvi>
#define pii pair<int,int>
#define vpii vector<pii>
#define vvpii vector<vpii>
#define fi first
#define se second
#define gcd __gcd
#define ld long double
#define ll long long
#define ull unsigned long long
#define MP make_pair
#define endl "\n"
//#define int ll
//-------------------------------------------------------------------------------------------------------//
int readInt(){
char c;
do{
c = getchar();
}while(c!='-' && !isdigit(c));
bool neg = (c=='-');
int res = neg?0:c-'0';
while(isdigit(c=getchar())) res = (res<<3)+(res<<1)+(c-'0');
return neg?-res:res;
}
//-------------------------------------------------------------------------------------------------------//
template<typename T> bool mini(T &a, const T &b){if(a>b){a=b;return true;}return false;}
template<typename T> bool maxi(T &a, const T &b){if(a<b){a=b;return true;}return false;}
//-------------------------------------------------------------------------------------------------------//
const int MAXN = 4e3+123;
const int MOD = 1e9+7;
const int INF = 1e9;
const int LOG = 16;
const ll LINF = 5e17;
const ld EPS = 1e-9;
const ld PI = acos(-1);
//-------------------------------------------------------------------------------------------------------//
int a[MAXN][MAXN];
int n,m,k;
namespace sub1{
void solve(){
REP(l,1,n){
int ok = 1;
REP(i,1,n){
if(i==l) continue;
int cnt = 0;
REP(j,1,m) if(a[l][j]!=a[i][j]) ++cnt;
if(cnt!=k){
ok = 0;
break;
}
}
if(ok){
cout << l;
return ;
}
}
}
}
namespace sub2{
bitset<MAXN> f[MAXN];
void solve(){
REP(i,1,n) REP(j,1,m) f[i][j] = a[i][j]-1;
REP(l,1,n){
int ok = 1;
REP(i,1,n){
if(i==l) continue;
int cnt = (f[l]^f[i]).count();
if(cnt!=k){
ok = 0;
break;
}
}
if(ok){
cout << l;
return ;
}
}
}
}
void solve(){
cin >> n >> m >> k;
int s2 = 1;
REP(i,1,n){
REP(j,1,m){
char ch; cin >> ch;
if(ch=='A') a[i][j] = 1;
if(ch=='C') a[i][j] = 2;
if(ch=='G') a[i][j] = 3;
if(ch=='T') a[i][j] = 4;
if(a[i][j]>2) s2 = 0;
}
}
if(s2){
sub2::solve();
return ;
}
sub1::solve();
}
signed main(){
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
#define task "test"
if(fopen(task".inp","r")){
freopen(task".inp","r",stdin);
freopen(task".out","w",stdout);
}
#define task1 "nothing"
if(fopen(task1".inp","r")){
freopen(task1".inp","r",stdin);
freopen(task1".out","w",stdout);
}
int test = 1;
while(test--){
solve();
cout << endl;
}
return 0;
}
