func_code_string: #include <bits/stdc++.h>   int read() {     static int c, x;     while ((c = getchar()) < 48) {     }     x = c & 15;     while ((c = getchar()) >= 48) x = x * 10 + (c & 15);     return x;   }   struct edge {     int next, to;   } e[100010 << 1];   int ans = 0;   int head[100010], deg[100010], f0[100010], f1[100010];   inline void add(const int &x, const int &y) {     static int ei;     e[++ei].next = head[x];     e[ei].to = y;     head[x] = ei;     ++deg[x];   }   void dfs(const int &x, const int &fa) {     f1[x] = 1;     f0[x] = deg[x] - 1;     for (int i = head[x]; i; i = e[i].next) {       const int y = e[i].to;       if (y != fa) {         dfs(y, x);         ans = std::max(ans, f0[x] + std::max(f0[y], f1[y]));         ans = std::max(ans, f1[x] + f0[y]);         f0[x] = std::max(f0[x], std::max(f0[y], f1[y]) + deg[x] - 2);         f1[x] = std::max(f1[x], f0[y] + 1);       }     }   }   int main() {     const int n = read();     for (int i = n; --i;) {       const int x = read(), y = read();       add(x, y);       add(y, x);     }     dfs(1, 0);     printf( %d n , ans);     return 0;   }   