#include <iostream>
#include <stdio.h>
using namespace std;

void f(int x,int y,int d){
	if(x+y<d){
		printf("0\n");
		return ;
	}
	if(x>y){
		int t=x;
		x=y;
		y=t;
	}
	if(d<=x){
		printf("%d\n",d+1);
	}else if(d<=y){
		printf("%d\n",x+1);
	}else{
		printf("%d\n",x+y-d+1);
	}
}	

int main() {
	// your code goes here
	int x,y,d;
	scanf("%d %d %d",&x,&y,&d);
	f(x,y,d);
	return 0;
}