View Compilation Error

0_0_21795523_5659.cpp: In function 'long long int fast(long long int, long long int)':
0_0_21795523_5659.cpp:22:25: error: 'mod' was not declared in this scope
             ans=(ans*a)%mod;
                         ^
0_0_21795523_5659.cpp:24:17: error: 'mod' was not declared in this scope
         a=(a*a)%mod;
                 ^
0_0_21795523_5659.cpp: In function 'int main()':
0_0_21795523_5659.cpp:41:21: error: 'mod' was not declared in this scope
             a=(a*i)%mod;
                     ^
0_0_21795523_5659.cpp:45:21: error: 'mod' was not declared in this scope
             b=(b*i)%mod;
                     ^
0_0_21795523_5659.cpp:48:21: error: 'mod' was not declared in this scope
             b=(b*i)%mod;
                     ^
0_0_21795523_5659.cpp:50:18: error: 'mod' was not declared in this scope
         b=fast(b,mod-2);
                  ^