View Compilation Error

0_0_30132662_11052.cpp: In function 'int main()':
0_0_30132662_11052.cpp:25:20: error: 'cha' was not declared in this scope
             ans+=a[cha];ans%=mod;
                    ^
0_0_30132662_11052.cpp:30:28: error: 'cha' was not declared in this scope
             if(x==1) ans=a[cha+1];
                            ^
0_0_30132662_11052.cpp:31:24: error: 'cha' was not declared in this scope
             else ans=a[cha];
                        ^