View Compilation Error

0_0_32904044_24543.cpp: In function 'int main()':
0_0_32904044_24543.cpp:170:19: error: 'mod' was not declared in this scope
       t=(t+sb[i])%mod;
                   ^
0_0_32904044_24543.cpp:172:26: error: 'mod' was not declared in this scope
      sb[i]=(sb[i]+sb[i])%mod;
                          ^
0_0_32904044_24543.cpp:175:17: error: 'mod' was not declared in this scope
     ans=(ans+t)%mod;  
                 ^