View Compilation Error

0_0_29993023_28175.cpp: In function 'int solve(int)':
0_0_29993023_28175.cpp:24:26: error: 'sort' was not declared in this scope
  sort(G + 1, G + sz, cmp2);
                          ^
0_0_29993023_28175.cpp: In function 'int main()':
0_0_29993023_28175.cpp:32:30: error: 'sort' was not declared in this scope
   sort(G + 1, G + n + 1, cmp1);
                              ^