func_code_string: #include <bits/stdc++.h>   using namespace std;   struct edge {     int v, nxt;   } e[2050];   int ecnt;   int n, m;   int totdep;   int pw[2050];   map<int, int> head;   map<int, bool> has_fa;   map<int, int> sz;   map<int, bool> vis;   void adde(int u, int v) {     e[++ecnt].v = v;     e[ecnt].nxt = head[u];     head[u] = ecnt;   }   int getdep(int pos) { return pos == 0 ? 0 : getdep(pos / 2) + 1; }   int getsz(int pos) {     int curdep = getdep(pos);     int tmp = curdep;     int lc = pos, rc = pos;     while (curdep < totdep) {       curdep++;       lc = lc << 1;       rc = rc << 1 | 1;     }     if (n < lc)       return pw[totdep - tmp - 1];     else if (n > rc)       return pw[totdep - tmp];     else       return pw[totdep - tmp - 1] + n - lc + 1;   }   int us[2050], vs[2050];   int seq[2050], scnt;   long long ans;   const int mod = 1000000007;   void mark(int pos) {     while (pos / 2) {       if (has_fa[pos]) return;       has_fa[pos] = 1;       seq[++scnt] = pos;       pos = pos / 2;     }   }   void dfs_sz(int pos) {     sz[pos] = getsz(pos);     if (has_fa[pos << 1]) dfs_sz(pos << 1), sz[pos] -= getsz(pos << 1);     if (has_fa[pos << 1 | 1])       dfs_sz(pos << 1 | 1), sz[pos] -= getsz(pos << 1 | 1);   }   int cur;   void dfs_solv(int pos) {     vis[pos] = 1;     ans += 1ll * cur * sz[pos] % mod;     ans %= mod;     if (!vis[pos << 1] && has_fa[pos << 1]) dfs_solv(pos << 1);     if (!vis[pos << 1 | 1] && has_fa[pos << 1 | 1]) dfs_solv(pos << 1 | 1);     if (!vis[pos >> 1] && (pos >> 1)) dfs_solv(pos >> 1);     for (int i = head[pos]; i; i = e[i].nxt) {       int v = e[i].v;       if (!vis[v]) dfs_solv(v);     }     vis[pos] = 0;   }   int main() {     scanf( %d%d , &n, &m);     if (m == 0) {       printf( %lld n , n * 1ll * n % mod);       return 0;     }     seq[++scnt] = 1;     totdep = getdep(n);     pw[0] = 1;     for (int i = 1; i <= 1000; ++i) pw[i] = pw[i - 1] * 2 + 1;     for (int i = 1; i <= m; ++i) {       scanf( %d%d , &us[i], &vs[i]);       mark(us[i]);       mark(vs[i]);       adde(us[i], vs[i]);       adde(vs[i], us[i]);     }     dfs_sz(1);     for (int i = 1; i <= scnt; ++i) {       cur = sz[seq[i]];       dfs_solv(seq[i]);     }     printf( %lld n , ans);   }   