View Compilation Error

0_0_5561639_5137.cpp: In function `int factor(int)':
0_0_5561639_5137.cpp:21: error: `judge' undeclared (first use this function)
0_0_5561639_5137.cpp:21: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_5561639_5137.cpp: In function `int judge(int, int)':
0_0_5561639_5137.cpp:27: error: `int judge(int, int)' used prior to declaration