View Compilation Error

0_0_38639335_26750.cpp: In function 'void solve()':
0_0_38639335_26750.cpp:23:25: error: 'mpd' was not declared in this scope
             cout<<((n-m+mpd)/2)%mod<<endl;
                         ^~~
0_0_38639335_26750.cpp:23:25: note: suggested alternative: 'mod'
             cout<<((n-m+mpd)/2)%mod<<endl;
                         ^~~
                         mod