/in/foo.cc: In function 'int main()':
/in/foo.cc:27:21: error: lvalue required as left operand of assignment
         f[j+a[i]=f[j];
                     ^
/in/foo.cc:27:22: error: expected ']' before ';' token
         f[j+a[i]=f[j];
                      ^
/in/foo.cc:25:9: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
       if(f[j]>0)
         ^