#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define For(i,a,b) for(int i=(a);i<=(b);i++)
#define dFor(i,a,b) for(int i=(a);i>=(b);i--)
#define tomin(x,y) x=min(x,y)
#define tomax(x,y) x=max(x,y)
#define abs_(x) max(x,-(x)) 
#define pb push_back 
#define gc getchar
#define ull unsigned long long
const int N=1e5+5,P=1e9+21,B=131;
ll read()
{
	ll x=0,y=1; char c=gc();
	for(;!isdigit(c);c=gc()) if(c=='-') y=0;
	for(;isdigit(c);c=gc()) x=(x<<3)+(x<<1)+(c^48);
	return y?x:-x;
}
char getc() { char c=gc(); for(;!isalpha(c)&&!isdigit(c);c=gc()) ; return c; }
void out(ll x) { if(x>9) out(x/10); putchar(x%10+'0'); }
int n,m,K;
ull a[N];
string ch[N];
ull s[N][5],sum;
mt19937 rnd(26);
int main()
{
	n=read(),m=read(),K=read();
	For(i,1,n)
	{
		a[i]=rnd()*1ll<<32|rnd();
		ch[i]=' ';
		For(j,1,m)
		{
			int t=getc()-'A';
			ch[i]+=t+'A';
			s[j][t]+=a[i];
		}
		sum+=a[i];
	}
	
	For(i,1,n)
	{
		ll t=0;
		For(j,1,m)
		{
			t+=s[j][ch[i][j]-'A']-a[i];
		}
		if(t==(sum-a[i])*(m-K)) 
		{
			printf("%d\n",i);
			return 0;
		}
	}
	return 0;
}
/*

*/