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OI-codes/AtCoder/ABC255/C/C.cpp

55 lines
1.4 KiB
C++

#include <iostream>
#include <algorithm>
#include <cmath>
using std::cin;
using std::cout;
const char endl = '\n';
long long x, a, d, n;
int main() {
std::ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> x >> a >> d >> n;
if (d > 0) {
if (x <= a) {
cout << std::abs(a - x) << endl;
} else if (x >= a + (n - 1) * d) {
cout << std::abs(x - a - (n - 1) * d) << endl;
} else {
long long k = (x - a) / d;
cout << std::min({
std::abs(a + k * d - x),
std::abs(a + (k - 1) * d - x),
std::abs(a + (k + 1) * d - x),
std::abs(a + (k - 2) * d - x),
std::abs(a + (k + 2) * d - x),
})
<< endl;
}
} else {
if (x >= a) {
cout << std::abs(x - a) << endl;
} else if (x <= a + (n - 1) * d) {
cout << std::abs(a + (n - 1) * d - x) << endl;
} else {
long long k = (x - a) / d;
cout << std::min({
std::abs(a + k * d - x),
std::abs(a + (k - 1) * d - x),
std::abs(a + (k + 1) * d - x),
std::abs(a + (k - 2) * d - x),
std::abs(a + (k + 2) * d - x),
})
<< endl;
}
}
return 0;
}