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#include <cstdlib>
#include <iostream>
#include <sstream>
#include "boost/format.hpp"

using namespace std;
using namespace boost;

string &center( string &str, int width ){
   int len = str.length();
   if( len > width ){
      str = str.substr( (len-width+1)/2, width );
   }
   ostringstream oss;
   oss << "%1$=" << width << "s";
   str = ( format(oss.str()) % str ).str();
   return str;
}

int main ( int argc, char *argv[] ){
   int width( atoi(argv[2]) );
   string str( argv[1] );
   cout << center( str, width ) << endl;
   return EXIT_SUCCESS;
}