View Compilation Error

0_0_6762245_20979.cpp: In function `void init()':
0_0_6762245_20979.cpp:15: error: `c' undeclared (first use this function)
0_0_6762245_20979.cpp:15: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_6762245_20979.cpp:16: error: `N' undeclared (first use this function)
0_0_6762245_20979.cpp: In function `int f(int, int)':
0_0_6762245_20979.cpp:37: error: `c' undeclared (first use this function)