#include <stdio.h>#include <string.h>int maxstep;int s[100][100];int n, m;void dfs(int v, int c){    int i;    if(maxstep < c)        maxstep = c;    for(i = 0; i < n; i++)    {        if(s[v][i] && s[i][v] && i != v)        {            s[v][i] = 0;            dfs(i, c + 1);            s[v][i] = 1;        }    }}int main(int argc, char *argv[]){    int i, v1, v2;    for(; scanf("%d%d", &n, &m) != EOF && n + m; printf("%d\n", maxstep))    {        memset(s, 0, sizeof(s));        for(i = 1; i <= m; i++)        {            scanf("%d%d", &v1, &v2);            s[v1][v2] = s[v2][v1] = 1;        }        maxstep = -1;        for(i = 0; i < n; i++)            dfs(i, 0);    }    return 0;}