'use strict';

const main = (input) => {
    const K = parseInt(input, 10);
    // K=2..100
    const oddCount = Math.floor(K / 2);
    const evenCount = Math.floor((K + 1) / 2);
    const result = oddCount * evenCount;
    console.log(result);
};

const isTest = false;

if (isTest) {
    main('3');
    main('6');
    main('11');
    main('50');
} else {
    main(require('fs').readFileSync('/dev/stdin', 'utf8'));
}