#include<iostream>
#include<cstdio>
#include<ctime>
#define N 20000000
using namespace std;
int read()
{
    char c=0;
    int sum=0;
    while (c<'0'||c>'9') c=getchar();
    while ('0'<=c&&c<='9') sum=sum*10+c-'0',c=getchar();
    return sum;
}
int n,m,k;
char c[N+1];
unsigned long long seed=time(0),rd[N+1],dp[4],delta[N+1],res;
int F(int x,int y)
{
    return (x-1)*m+y;
}
unsigned long long RAND()
{
    seed=(seed<<7)^seed;
    seed=(seed>>13)^seed;
    seed=(seed<<17)^seed;
    return seed;
}
int main()
{
    n=read(),m=read(),k=read();
    for (int i=1;i<=n;++i) rd[i]=RAND(),res+=rd[i]*k;
    for (int i=1;i<=n;++i)
	for (int j=1;j<=m;++j)
	    cin>>c[F(i,j)];
    for (int i=1;i<=m;++i)
    {
	for (int j=0;j<=3;++j) dp[j]=0;
	for (int j=1;j<=n;++j)
	    for (int k=0;k<=3;++k)
		if (c[F(j,i)]-'A'!=k)
		    dp[k]=dp[k]+rd[j];
	for (int j=1;j<=n;++j) delta[j]+=dp[c[F(j,i)]-'A'];
    }
    for (int i=1;i<=n;++i)
	if (delta[i]==res-rd[i]*k)
	{
	    printf("%d\n",i);
	    return 0;
	}
    return 0;
}