View Compilation Error

0_0_38590625_22646.cpp: In function 'int main()':
0_0_38590625_22646.cpp:110:10: error: 'res' was not declared in this scope
    cout<<res<<endl;
          ^~~
0_0_38590625_22646.cpp:110:10: note: suggested alternative: 'gets'
    cout<<res<<endl;
          ^~~
          gets