var readline = require('readline');
var rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
    terminal: false
});

rl.on('line', function (line) {
    const arr = line.split(' ').map(x => Number(x));
    let n = arr[0];
    let x = arr[1];
    let t = arr[2];
    console.log(Math.ceil(n/x)*t);
});
