foo.cc: In function 'int main()':
foo.cc:11:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<x.size();i++) if(int(x[i])>=65 && int(x[i])<=90) x[i]=char(int(x[i])+32);
              ~^~~~~~~~~
foo.cc:14:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<x.size()-1;i++) for(int j=i+1;j<x.size()-1;j++) if(x[i]==x[j] && x[i+1]==x[j+1]) p[j]++;
              ~^~~~~~~~~~~
foo.cc:14:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<x.size()-1;i++) for(int j=i+1;j<x.size()-1;j++) if(x[i]==x[j] && x[i+1]==x[j+1]) p[j]++;
                                              ~^~~~~~~~~~~
foo.cc:15:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<x.size()-1;i++) if(p[i]>maxn) maxn=p[i];
              ~^~~~~~~~~~~
foo.cc:18:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<x.size()-1;i++)
              ~^~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务