第17行CE

#include<bits/stdc++.h>
int k,n,m;
int pos[50005];
bool chk(int mid){
    int ans=0,st=0;
    for(int i=1;i<=n;++i){
    	if(pos[i]-st<mid){
        	ans=ans+1;
		}
        else{
        	st=pos[i];
		} 
	}
    return ans<=m;
}
int main(){
    cin>>k>>n>>m;
    for(int i=1;i<=n;++i){
    	cin>>pos[i];
	}
    int l=0,r=k,mid;
    while(l<r){
        mid=(l+r)/2;
        if(check(mid)){
        	l=mid+1;
		}
        else{
        	r=mid-1;
		} 
    }
    cout<<l-(!chk(l));
    return 0;
}