View Compilation Error

0_0_24701005_9806.cpp: In function 'll powmod(ll, ll)':
0_0_24701005_9806.cpp:12:51: error: 'assert' was not declared in this scope
 ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
                                                   ^
0_0_24701005_9806.cpp: In function 'int linear_seq::solve(ll, VI, VI)':
0_0_24701005_9806.cpp:27:28: error: 'assert' was not declared in this scope
         assert(SZ(a)==SZ(b));
                            ^