View Compilation Error

0_0_32759599_4201.cpp: In function 'void _Polynomial::DFT(int*, int, int)':
0_0_32759599_4201.cpp:46:9: error: 'i' was not declared in this scope
     FOR(i, 0, n - 1)a[i] = (LL)a[i] * I % MOD;
         ^
0_0_32759599_4201.cpp:46:20: error: 'FOR' was not declared in this scope
     FOR(i, 0, n - 1)a[i] = (LL)a[i] * I % MOD;
                    ^