View Compilation Error

0_0_37831530_26994.cpp: In function 'int main()':
0_0_37831530_26994.cpp:17:17: error: 'a' was not declared in this scope
    scanf("%d", &a[i]);
                 ^
0_0_37831530_26994.cpp:41:21: error: 'r' was not declared in this scope
     s = s.set()>>(N-r-1);
                     ^
0_0_37831530_26994.cpp:45:23: error: 'l' was not declared in this scope
     f = low^(high>>(r-l+1));
                       ^
0_0_37831530_26994.cpp:60:12: error: 'a' was not declared in this scope
     res ^= a[i];
            ^