Time Exceeded
/in/foo.cc: In function 'int main()':
/in/foo.cc:15:5: warning: operation on 'n' may be undefined [-Wsequence-point]
   a[--n]=(a[n]+a[n-1])/k;
     ^~~
/in/foo.cc:15:5: warning: operation on 'n' may be undefined [-Wsequence-point]
  /in/foo.cc: In function 'int main()':
/in/foo.cc:15:5: warning: operation on 'n' may be undefined [-Wsequence-point]
   a[--n]=(a[n]+a[n-1])/k;
     ^~~
/in/foo.cc:15:5: warning: operation on 'n' may be undefined [-Wsequence-point]