View Compilation Error

0_0_13431793_29185.cpp: In function 'void merge_x(int, int, int)':
0_0_13431793_29185.cpp:27:7: error: 'k' was not declared in this scope
  for( k=start;k<=end;k++)
       ^
0_0_13431793_29185.cpp: In function 'void merge_y(int, int, int)':
0_0_13431793_29185.cpp:51:7: error: 'k' was not declared in this scope
  for( k=start;k<=end;k++)
       ^