View Compilation Error

0_0_27220814_21450.cpp: In function 'int main()':
0_0_27220814_21450.cpp:13:3: error: 'len1' was not declared in this scope
   len1=strlen(num1)-1;
   ^
0_0_27220814_21450.cpp:14:3: error: 'len2' was not declared in this scope
   len2=strlen(num2)-1;
   ^