#include<stdio.h>

#define ABS(a) ((a)>=0?(a):-(a))
#define MIN(a,b) ((a)<(b)?(a):(b))

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

  int s=MIN(x,y);
  int t=x+y-s;

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

int main(void){
  run();
  return 0;
}