A. Soldier and Bananas(CF546) Codeforces Round #304 (Div. 2)
A. Soldier and Bananas
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output
A soldier wants to buy w bananas in the shop. He has to pay k dollars
for the first banana, 2k dollars for the second one and so on (in other words, he has to pay i·k dollars
for the i-th banana).
He has n dollars. How many dollars does he have to borrow from his friend soldier to buy w bananas?
Input
The first line contains three positive integers k, n, w (1 ≤ k, w ≤ 1000, 0 ≤ n ≤ 109),
the cost of the first banana, initial number of dollars the soldier has and number of bananas he wants.
Output
Output one integer — the amount of dollars that the soldier must borrow from his friend. If he doesn't have to borrow money, output 0.
Sample test(s)
input
3 17 4
output
13
#include <stdio.h>
#include <string.h>
#include <algorithm>
using namespace std;
#define LL __int64
LL n,k,w;
int main()
{
int i;
LL sum = 0;
scanf("%I64d%I64d%I64d",&k,&n,&w);
for(i = 1;i<=w;i++)
sum +=i*k;
if(n>=sum)
printf("0\n");
else
printf("%I64d\n",sum-n);
return 0;
}
