/in/foo.cc: In function 'int main()':
/in/foo.cc:18:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(k=0;k<=a[i-j].length()-1;k++)
            ~^~~~~~~~~~~~~~~~~~~
/in/foo.cc:21:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
       if(k==a[i-j].length()&&s[i-j]>=s[i])
          ~^~~~~~~~~~~~~~~~~
/in/foo.cc:6:8: warning: unused variable 'm' [-Wunused-variable]
  int n,m,i,j,k,max;
        ^
/in/foo.cc:6:16: warning: unused variable 'max' [-Wunused-variable]
  int n,m,i,j,k,max;
                ^~~