function Main(input) {
    input = input.trim().split("\n").map(function(x) { return x.split(" ")});
    let N = parseInt(input[0][0], 10);
    let X = parseInt(input[0][1], 10);
    let T = parseInt(input[0][2], 10);
    if (N % X === 0) console.log(T * N / X );
    else console.log(Math.ceil(N / X) * T);
}

Main(require("fs").readFileSync("/dev/stdin", "utf8"));
