shoes.cpp: In function 'long long int count_swaps(std::vector<int>)':
shoes.cpp:5:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<s.size()/2;i++){
              ~^~~~~~~~~~~
shoes.cpp:6:13: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   if(s[i]<0 && i%2==1 || s[i]>0 && i%2==0) ans++;