View Compilation Error

0_0_25711668_6923.cpp:6:1: error: expected initializer before 'int'
 int ans[maxn];
 ^
0_0_25711668_6923.cpp: In function 'int main()':
0_0_25711668_6923.cpp:33:30: error: 'num' was not declared in this scope
         for(int i=0;i<n;++i) num[i]=rng61();
                              ^
0_0_25711668_6923.cpp:41:17: error: 'ans' was not declared in this scope
                 ans[b[i].id]=ans[b[i+1].id];
                 ^
0_0_25711668_6923.cpp:44:25: error: 'num' was not declared in this scope
             nth_element(num,num+b[i].num,num+b[i+1].num);
                         ^
0_0_25711668_6923.cpp:45:13: error: 'ans' was not declared in this scope
             ans[b[i].id]=num[b[i].num];
             ^
0_0_25711668_6923.cpp:48:38: error: 'ans' was not declared in this scope
         for(int i=0;i<m;++i) cout << ans[i] << (i==m-1?'\n':' ');
                                      ^