#include <bits/stdc++.h> using namespace std;

int main() { int m, n, h, cnt = 0, a = 0; cin >> m >> n >> h; for (int i = 0; i <= h; i + m - n) { a = a + i; if (i <= h) { cnt = cnt + 1; } if (i + m >= h) {

	}
	cout << cnt;
	break;
}

return 0;

}