View Compilation Error

0_0_18162589_142.cpp: In function 'int main()':
0_0_18162589_142.cpp:11:27: error: 'mod' was not declared in this scope
         san[i]=san[i-1]*3%mod;
                           ^
0_0_18162589_142.cpp:17:45: error: 'mod' was not declared in this scope
             c[i][j]=(c[i-1][j-1]+c[i-1][j])%mod;
                                             ^
0_0_18162589_142.cpp:30:64: error: 'mod' was not declared in this scope
                     dp[i][j]=(dp[i][j]-dp[ti+1][tj]*c[i-1][ti]%mod*c[j][tj]%mod*san[(i-1-ti)*(j-tj)])%mod;
                                                                ^