#include <cstdio>
#include <cmath>
#define rep( i, n, m ) for(int i = ( n ); i < ( m ); i++)

typedef long long int ll;

int main( void ){
	ll a, b, c;
	if (!scanf( "%lld %lld %lld", &a, &b, &c ))
		return 0;
	ll sum = c;
	if (c>=a)
		sum--;
	if (c>=b)
		sum--;
	if (sum < 0)
		sum = 0;
	printf("%lld\n", sum);
	return 0;
}