process.stdin.resume();
process.stdin.setEncoding('utf8');
// 自分の得意な言語で
// Let's チャレンジ！！

var lines = [];
var reader = require('readline').createInterface({
  input: process.stdin,
  output: process.stdout
});
reader.on('line', (line) => {
  lines.push(line);
});
reader.on('close', () => {
 var L = parseInt(lines[0].split(' ')[0],10);
 var H = parseInt(lines[0].split(' ')[1],10);
 var b = parseInt(lines[0].split(' ')[2],10);
var count = 0;
  
  for(var i=L;i<=H;i++){
  	if(i%b === 0){
    	count++;
    }
  }
console.log(count);
  
});