View Compilation Error

0_0_32839272_28722.cpp: In function 'void u(int, int)':
0_0_32839272_28722.cpp:13:7: error: 'k' was not declared in this scope
  if(f[k]==f[j]) return ;
       ^
0_0_32839272_28722.cpp:13:13: error: 'j' was not declared in this scope
  if(f[k]==f[j]) return ;
             ^