/in/foo.cc: In function 'int link(int, int)':
/in/foo.cc:23:1: warning: no return statement in function returning non-void [-Wreturn-type]
 }
 ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:45:9: warning: unused variable 'ans' [-Wunused-variable]
     int ans=0,s=0;
         ^~~
/in/foo.cc:44:33: warning: iteration 1009 invokes undefined behavior [-Waggressive-loop-optimizations]
     for(int i=1;i<=MAXN;i++)f[i]=i;
                             ~~~~^~
/in/foo.cc:44:18: note: within this loop
     for(int i=1;i<=MAXN;i++)f[i]=i;
                  ^