/in/foo.cc: In function 'int check(int)':
/in/foo.cc:22:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 1; i <= cur.length(); i++) dd[i] = dd[i - 1] * mod + cur[i-1];
                  ~~^~~~~~~~~~~~~~~
/in/foo.cc:24:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = mid; i < s[x].length(); i++) jian = jian*mod + s[x][i];
                    ~~^~~~~~~~~~~~~~~
/in/foo.cc:26:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = mid; i <= cur.length(); i++)
                    ~~^~~~~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:47:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = 0; j < t[i].length(); j++)
                   ~~^~~~~~~~~~~~~~~