#include<stdlib.h>
#include<stdio.h>
#define maxsize 100
typedef struct{
    int data[maxsize];
    int length;
}List;

int SearchList(List &L,int e){
    int min =0;int max=L.length-1;int mean=(max+min)/2;
    if(L.data[min]==e){return min+1;}
    if(L.data[max]==e){return max+1;}
    while(L.data[mean]!=e && min+1<max){
        if(L.data[mean]<e){min=mean;mean=(max+min)/2;}
        if(L.data[mean]>e){max=mean;mean=(max+min)/2;}
    }
    if(L.data[mean]==e){return mean;}
    else{return -1;}
}

int main(){
    List L;L.length=0;
    for(int i=0;i<maxsize;i++){L.data[i]=i;L.length++;}
    int i=SearchList(L,30);
    printf("%d\n",i);
    return 0;
    
}