#include <bits/stdc++.h>
#ifdef LOCAL
#include <bits/debug.hpp>
#endif // LOCAL
#define ll long long
#define all(x) x.begin(), x.end()
#define Neco "Genetics"
#define resp(x) sort(all(x)), x.resize(unique(all(x)) - x.begin())
#define getbit(x,i) ((x >> i)&1)
#define _left id * 2, l, mid
#define _right id * 2 + 1, mid + 1, r
#define cntbit(x) __builtin_popcountll(x)
#define fi(i, a, b) for(int i = a; i <= b; i++)
#define fid(i, a, b) for(int i = a; i >= b; i--)
#define maxn (int) 4102
using namespace std;
const ll mod = 1e9 + 7; //972663749
const ll base = 911382323;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll GetRandom(ll l, ll r) {
return uniform_int_distribution<ll> (l, r)(rng);
}
int n, m, k;
char a[maxn][maxn];
ll Rnd[maxn], P[maxn];
ll S[maxn];
void solve()
{
cin >> n >> m >> k;
fi(i, 1, n) fi(j, 1, m) cin >> a[i][j];
fi(j, 1, m)
{
ll All = 0;
S['A'] = S['G'] = S['T'] = S['C'] = 0;
fi(i, 1, n) {
All += Rnd[i];
S[a[i][j]] += Rnd[i];
}
fi(i, 1, n) P[i] += All - S[a[i][j]];
}
ll Sum = 0;
fi(i, 1, n) Sum += 1ll * Rnd[i] * k;
fi(i, 1, n) {
ll w = 1ll * Rnd[i] * k;
if(P[i] == Sum - w) return cout << i, void();
}
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
if(fopen(Neco".inp", "r")) {
freopen(Neco".inp", "r", stdin);
freopen(Neco".out", "w", stdout);
}
fi(i, 1, maxn - 2) Rnd[i] = GetRandom(1, 1e18);
int nTest = 1;
// cin >> nTest;
while(nTest--)
{
solve();
}
return 0;
}
