// Hydro submission #66f2b1f19b5bc274203286be@1727181298235
#include<bits/stdc++.h>
using namespace std;
#define ve vector
#define x first
#define y second
#define ep emplace
#define pb emplace_back
#define de(b) #b,'=',b
#define Sz(k) int((k).size())
#define all(b) begin(b),end(b)
#define rll(k) rbegin(k),rend(k)
namespace BK0717 {
#ifdef Bella
ifstream cin("BK.in");ofstream cout("BK.out");
void clg(auto x){cerr<<x;}void clg(auto x,auto...y){clg(x),clg(y...);}
#endif
int cn(auto&x,auto y){return x>y?x=y,1:0;}
int cx(auto&x,auto y){return x<y?x=y,1:0;}
using LL=long long;using db=double;using pii=pair<int,int>;using ull=unsigned long long;
void Solve() {
  mt19937 Y(random_device{}());
  int n,m,K; cin>>n>>m>>K;
  ve<ull>a(n);
  ve<string>s(n);
  ve<array<ull,4>>f(m);
  for(int i=0;i<n;++i) {
    cin>>s[i];
    a[i]=uniform_int_distribution<LL>(1,(LL)46e17)(Y);
    for(int j=0;j<m;++j) f[j][s[i][j]-'A']+=a[i];
  }
  const ull tot=accumulate(all(a),0ULL);
  for(int i=0;i<n;++i) {
    ull sum=0;
    for(int j=0;j<m;++j) sum+=f[j][s[i][j]-'A'];
    if((m-K)*tot+K*a[i]==sum) {
      cout<<(i+1);
      return;
    }
  }
  assert(0);
  return;
}
void main() {
  ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
  int T=1;
  // cin>>T;
  for(;T--;) Solve();
} }
main(){BK0717::main();}