func_code_string: #include <bits/stdc++.h>   const long long base1 = 131;   const long long base2 = 233;   const long long mod1 = 998244353;   const long long mod2 = 1e9 + 7;   const long long MaxN = 1e6 + 50;   template <class t>   inline void read(t &s) {     s = 0;     register long long f = 1;     register char c = getchar();     while (!isdigit(c)) {       if (c ==  - ) f = -1;       c = getchar();     }     while (isdigit(c)) s = (s << 3) + (s << 1) + (c ^ 48), c = getchar();     s *= f;     return;   }   template <class t, class... A>   inline void read(t &x, A &...a) {     read(x);     read(a...);   }   template <class t>   inline void write(t x) {     if (x < 0) putchar( - ), x = -x;     long long buf[21], top = 0;     while (x) buf[++top] = x % 10, x /= 10;     if (!top) buf[++top] = 0;     while (top) putchar(buf[top--] ^  0 );     return;   }   inline void setIn(std::string s) {     freopen(s.c_str(),  r , stdin);     return;   }   inline void setOut(std::string s) {     freopen(s.c_str(),  w , stdout);     return;   }   inline void setIO(std::string s =   ) {     setIn(s +  .in );     setOut(s +  .out );     return;   }   template <class t>   inline bool checkmin(t &x, t y) {     if (x > y) {       x = y;       return 1;     }     return 0;   }   template <class t>   inline bool checkmax(t &x, t y) {     if (x < y) {       x = y;       return 1;     }     return 0;   }   inline long long lowbit(long long x) { return x & (-x); }   std::vector<long long> E[MaxN];   std::pair<long long, long long> f[MaxN];   long long e1[MaxN], e2[MaxN], U[MaxN], V[MaxN];   signed main(void) {     long long n, m;     read(n, m);     register long long u, v, ans = 0;     for (long long i = 1; i <= m; ++i)       read(u, v), U[i] = u, V[i] = v, E[u].push_back(v), E[v].push_back(u);     for (long long i = 1; i <= n; ++i) std::sort((E[i]).begin(), (E[i]).end());     for (long long i = 1; i <= n; ++i) {       register long long s1 = 0, s2 = 0;       for (auto v : E[i])         s1 = (s1 * base1 + v) % mod1, s2 = (s2 * base2 + v) % mod2;       f[i] = std::make_pair(s1, s2);       s1 = 0, s2 = 0;       E[i].push_back(i), std::sort((E[i]).begin(), (E[i]).end());       for (auto v : E[i])         s1 = (s1 * base1 + v) % mod1, s2 = (s2 * base2 + v) % mod2;       e1[i] = s1, e2[i] = s2;     }     std::sort(f + 1, f + n + 1);     register long long cnt = 0;     for (long long i = 2; i <= n; ans += cnt, ++i)       cnt = (f[i] == f[i - 1]) ? (cnt + 1) : 0;     for (long long i = 1; i <= m; ++i)       if (e1[U[i]] == e1[V[i]] && e2[U[i]] == e2[V[i]]) ++ans;     write(ans), std::puts(  );     return 0;   }   