#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vii;
typedef pair<int,int> pi;
typedef vector<pi> pii;
typedef tuple<int,int,int> ti;
typedef vector<ll> li;
typedef vector<li> lii;
#define REP(i,a,b) for(int i=a;i<b;i++)
#define F first
#define S second
#define PB push_back
#define LSOne(s) ((s)&(-s))
#define all(x) x.begin(),x.end()
ll INF=1000000000000000010;
int inf=1e9+10;
ll M=1e9+7;
int n,m,k;
vector<pair<string,int>> a;
vector<pair<bitset<4100>,int>> b,c,d,e;
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
cin>>n>>m>>k;
a.resize(n);b.resize(n);c.resize(n);d.resize(n);e.resize(n);
REP(i,0,n)cin>>a[i].F;
REP(i,0,n)a[i].S=i;
sort(all(a));
REP(i,0,n){
string s=a[i].F;
REP(j,0,m)if(s[j]=='A')b[i].F[j]=1;
REP(j,0,m)if(s[j]=='C')c[i].F[j]=1;
REP(j,0,m)if(s[j]=='T')d[i].F[j]=1;
REP(j,0,m)if(s[j]=='G')e[i].F[j]=1;
b[i].S=a[i].S;c[i].S=d[i].S;b[i].S=a[i].S;e[i].S=a[i].S;
}
REP(i,0,n){
bool flag=1;
REP(j,0,n)if(i!=j){
bitset<4100> X;
int cnt=0;
X=b[i].F^b[j].F;
cnt+=X.count();
X=c[i].F^c[j].F;
cnt+=X.count();
X=d[i].F^d[j].F;
cnt+=X.count();
X=e[i].F^e[j].F;
cnt+=X.count();
cnt/=2;
if(cnt!=k){
flag=0;
break;
}
}
if(flag){
cout<<b[i].S+1;
return 0;
}
}
}
