func_code_string: #include <bits/stdc++.h>   using namespace std;   int read() {     int num = 0;     bool f = 0;     char ch = getchar();     while (ch <  0  || ch >  9 ) {       f = (ch ==  - );       ch = getchar();     }     while (ch >=  0  && ch <=  9 ) {       num = (num << 1) + (num << 3) + ch -  0 ;       ch = getchar();     }     return f ? -num : num;   }   int n, m;   int deg[111];   vector<int> vec[111];   int topsort() {     int res = 0, fl = 1;     queue<int> Q;     while (fl) {       fl = 0;       for (int i = 1; i <= n; i++)         if (deg[i] == 1) Q.push(i), fl = 1;       while (!Q.empty()) {         int u = Q.front();         Q.pop();         deg[u]--;         for (int v : vec[u]) deg[v]--;       }       if (fl) res++;     }     return res;   }   int main() {     n = read(), m = read();     for (int i = 1; i <= m; i++) {       int x = read(), y = read();       deg[x]++, deg[y]++;       vec[x].push_back(y);       vec[y].push_back(x);     }     printf( %d n , topsort());     return 0;   }   