#include <stdio.h>

int main() {
	int x, y, d;
	scanf("%d %d %d", &x, &y, &d);

	int tx = (tx = d - x) > 0 ? tx : 0;
	int ty = (ty = d - y) > 0 ? ty : 0;
	int ans = (ans = d + 1 - (tx + ty)) > 0 ? ans : 0;

	printf("%d\n", ans);
	return 0;
}