View Compilation Error

0_0_18103738_216.cpp:5:7: error: 'mod' does not name a type
 const mod=10001;
       ^
0_0_18103738_216.cpp: In function 'int main()':
0_0_18103738_216.cpp:13:7: error: 'mod' was not declared in this scope
    a%=mod;
       ^