#include<bits/stdc++.h>
//#define int long long
#define ll long long
#define ull unsigned long long
#define ld long double
#define PII pair<int,int>
#define INF 0x3f3f3f3f
#define INFLL 0x3f3f3f3f3f3f3f3f
#define chkmax(a,b) a=max(a,b)
#define chkmin(a,b) a=min(a,b)
#define rep(k,l,r) for(int k=l;k<=r;++k)
#define per(k,r,l) for(int k=r;k>=l;--k)
#define cl(f,x) memset(f,x,sizeof(f))
using namespace std;
const int N=2e5+5,M=26;
mt19937 rd(time(0));
ull p[N],f[N][M];
string s[N];
signed main() {
    int n,m,k;
    scanf("%d%d%d",&n,&m,&k);
    ull tot=0,res=0;
    rep(i,1,n) {
        p[i]=rd();
        res+=k*p[i];
        tot+=m*p[i];
    }
    rep(i,1,n) {
        cin>>s[i];
        rep(j,0,m-1)
            f[j][s[i][j]-'A']+=p[i];
    }
    rep(i,1,n) {
        ull sum=0;
        rep(j,0,m-1)
            sum+=f[j][s[i][j]-'A'];
        if(tot-sum==res-k*p[i])
            return 0&printf("%d\n",i);
    }
    return 0;
}