View Compilation Error

0_0_29918521_14418.cpp:60:1: error: 'LL' does not name a type
 LL f(LL a,LL b,LL c,LL n)
 ^
0_0_29918521_14418.cpp: In function 'void init()':
0_0_29918521_14418.cpp:81:21: error: 'check' was not declared in this scope
         if(check(mid) < k)l = mid;
                     ^