View Compilation Error

0_0_7698423_12044.cpp: In function `long long int exp_mod2(long long int, long long int, long long int)':
0_0_7698423_12044.cpp:9: error: `exp_mod' undeclared (first use this function)
0_0_7698423_12044.cpp:9: error: (Each undeclared identifier is reported only once for each function it appears in.)