function main(input = "") {
    let arr = input.split(" ").map((v)=>(Number(v)));
    let N = arr[0], X  = arr[1], T = arr[2];

    let cnt = 0 | N / X
    if(N % X !== 0)
        cnt += 1;
        
    return cnt * T;
}

//******************************
exports.main = main;

function Main(input) {
    console.log(main(input.trim()));
}

if (process.argv[2] !== "test") {
    Main(require("fs").readFileSync("/dev/stdin", "utf8"));
}
