function ok(matrix: string[][], len: int, n: int, m: int) -> bool {
    let used:{string : int}={};
    for(let i = 0; i < m; i += 1) {
        let cur: string = "";
        for(let j = len; j < n; j += 1) {
            cur += matrix[j][i];
        }
        if(used.contains(cur)) {
            return false;
        }
        else {
            used[cur] = 1;
        }
    }
    return true;
}
function solve(input: string) -> string {
    let line = input.split("\n\n");

    let siz = line[0].split(" ");
    let n: int = int(siz[0]);
    let m: int = int(siz[1]);
    let matrix: string[][] = [];
    for(let i = 1; i <= n; i += 1) {
        matrix.push([]);
        for(let j = 0; j < m; j += 1) {
            matrix[i - 1].push(line[i][j]);
        }
    }

    let l: int = 0;
    let r: int = n;
    while(r - l > 1) {
        let mid: int = (r + l) / 2;
        if(ok(matrix, mid, n, m)) {
            l = mid;
        }
        else {
            r = mid;
        }
    }
    return string(l);
}