View Compilation Error

0_0_36577499_5745.cpp: In function 'void kmp()':
0_0_36577499_5745.cpp:42:2: error: 'len1' was not declared in this scope
  len1=strlen(ch);
  ^
0_0_36577499_5745.cpp:43:2: error: 'len2' was not declared in this scope
  len2=strlen(s);
  ^