/in/foo.cc: In function 'int main()':
/in/foo.cc:59:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int j=0;j<str.length();j++) if(str[j]<='Z'&&str[j]>='A') str[j]+='a'-'A';
                     ~^~~~~~~~~~~~~
/in/foo.cc:66:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i=0;i<str.length();i++) if(str[i]<='Z'&&str[i]>='A') str[i]+='a'-'A';
                     ~^~~~~~~~~~~~~
/in/foo.cc:69:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i=0;i<str.length();i++) if(str[i]<='Z'&&str[i]>='A') str[i]+='a'-'A';
                     ~^~~~~~~~~~~~~