Codeforces/546/a.cpp

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#include <iostream>
namespace {
using namespace std;
long pow(long base, long exp) {
if (exp == 0)
return 1;
long half = pow(base, exp / 2);
if (exp % 2 == 0)
return half * half;
return half * half * base;
}
int borrows(int k, int n, int w) {
int total = k * (1 + w) * w / 2;
return max(total - n, 0);
}
void solve() {
int k, n, w;
cin >> k >> n >> w;
cout << borrows(k, n, w) << "\n";
}
} // namespace
// for single test case, comment out for N test cases
#define SINGLE
#ifndef TEST
int main(void) {
#ifdef SINGLE
solve();
#else
// for multiple test cases
int N;
std::cin >> N >> std::ws;
for (auto i = 0; i < N; ++i) {
solve();
}
#endif
return 0;
}
#else
#include "../.common/cpp/catch_amalgamated.hpp"
TEST_CASE("examples") {
CHECK(borrows(3, 17, 4) == 13);
CHECK(borrows(3, 100, 4) == 0);
}
#endif