/in/foo.cc: In function 'int main()':
/in/foo.cc:46:5: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
  if (s1[b]) if (ans==-1) ans=s1[b];else ans=min(ans,s1[b]);
     ^
/in/foo.cc:47:5: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
  if (s2[a]) if (ans==-1) ans=s2[a];else ans=min(ans,s2[a]);
     ^