View Compilation Error

0_0_21381833_30945.cpp: In function 'void Solve()':
0_0_21381833_30945.cpp:37:6: error: expected primary-expression before 'int'
  fir(int i=n;i;i--)S[i]=S[i+1]+a[i];
      ^
0_0_21381833_30945.cpp:37:14: error: 'i' was not declared in this scope
  fir(int i=n;i;i--)S[i]=S[i+1]+a[i];
              ^