#include<stdio.h>

int main(){
    
    int X,Y,Z;
    int count = 0;
    scanf("%d %d %d",&X,&Y,&Z);
    
    while(X>0){
        if( Y<Z )   Y++;
        else        Z++;
        X--;
    }
    
    while(Y>0 && Z>0){
        Y--;
        Z--;
        count++;
    }
    
    printf("%d",count);
    
    return 0;
}