View Compilation Error

0_0_3270362_19195.cpp: In function `int main()':
0_0_3270362_19195.cpp:13: error: `c' undeclared (first use this function)
0_0_3270362_19195.cpp:13: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_3270362_19195.cpp: In function `int c(int, int)':
0_0_3270362_19195.cpp:21: error: `int c(int, int)' used prior to declaration