#include<bits/stdc++.h>
using namespace std;

namespace D {
    int n, m, k, x, y;
    char ch[201][2001];
    string str[201][201];
    struct info {
        int x;
        int y;
    };
    map<string, int> vis;
    map<string, info> ans;
    void work() {
        cin >> n >> m >> k;
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= m * k; j++) {
                cin >> ch[i][j];
            }
        }
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= m * k; j++) {
                str[i][((j + k - 1) / k)].push_back(ch[i][j]);
            }
        }
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= m; j++) {
                if (vis[str[i][j]] == 0) {
                    ans[str[i][j]] = {i, j};
                    vis[str[i][j]] = 1;
                } else {
                    vis[str[i][j]]++;
                }
            }
        }
        for (auto it = vis.begin(); it != vis.end(); it++) {
            if(it->second == 1) {
                cout << ans[it->first].x << ' ' << ans[it->first].y << '\n';
            }
        }
    }
}
int main (void) {
    ios::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    D::work();
    return 0;
}