Wrong Answer
/in/foo.cc: In function 'int main()':
/in/foo.cc:13:6: warning: operation on 'n' may be undefined [-Wsequence-point]
a[n--]=(a[n]+a[n-1])/k;
~^~
/in/foo.cc:13:6: warning: operation on 'n' may be undefined [-Wsequence-point]
/in/foo.cc: In function 'int main()':
/in/foo.cc:13:6: warning: operation on 'n' may be undefined [-Wsequence-point]
a[n--]=(a[n]+a[n-1])/k;
~^~
/in/foo.cc:13:6: warning: operation on 'n' may be undefined [-Wsequence-point]