1 /* 2 水题:ans = (1+2+3+...+n) * k - n,开long long 3 */ 4 #include <cstdio> 5 #include <algorithm> 6 #include <cstring> 7 #include <cmath> 8 using namespace std; 9 10 typedef long long ll; 11 12 int main(void) //Codeforces Round #304 (Div. 2) A. Soldier and Bananas 13 { 14 int k, n, w; 15 while (scanf ("%d%d%d", &k, &n, &w) == 3) 16 { 17 ll sum = (1 + w) * w / 2 * k; 18 if (sum < n) puts ("0"); 19 else printf ("%I64d\n", sum - n); 20 } 21 22 return 0; 23 } 24 25 26 /* 27 3 17 4 28 */