View Compilation Error

0_0_8462787_18255.cpp: In function `int main()':
0_0_8462787_18255.cpp:27: error: `len1' undeclared (first use this function)
0_0_8462787_18255.cpp:27: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_8462787_18255.cpp:28: error: `len2' undeclared (first use this function)