'use strict';

var _slicedToArray = function () { function sliceIterator(arr, i) { var _arr = []; var _n = true; var _d = false; var _e = undefined; try { for (var _i = arr[Symbol.iterator](), _s; !(_n = (_s = _i.next()).done); _n = true) { _arr.push(_s.value); if (i && _arr.length === i) break; } } catch (err) { _d = true; _e = err; } finally { try { if (!_n && _i["return"]) _i["return"](); } finally { if (_d) throw _e; } } return _arr; } return function (arr, i) { if (Array.isArray(arr)) { return arr; } else if (Symbol.iterator in Object(arr)) { return sliceIterator(arr, i); } else { throw new TypeError("Invalid attempt to destructure non-iterable instance"); } }; }();

var fs = require('fs');

var input = Buffer.alloc(0x10000);
fs.readSync(0, input, 0, 0x10000);

var _input$toString$split = input.toString().split('\n').map(function (n) {
  return parseInt(n);
}),
    _input$toString$split2 = _slicedToArray(_input$toString$split, 3),
    X = _input$toString$split2[0],
    A = _input$toString$split2[1],
    B = _input$toString$split2[2];

console.log((X - A) % B);