(function(stdin) {
  var lines  = stdin.toString().split('\n');
  var param = lines[0].split(' ').map(Number);
  var result = (function(a,b,c) {
    return [...Array(b - a + 1).key()]
      .map(v => v + a)
      .filter(v => v % c === 0)
      .length;
  }(param[0],param[1],param[2]
  ));
  console.log(result);
}(require('fs').readFileSync('/dev/stdin', 'utf8')));