神奇解法。

#include<bits/stdc++.h>
#define int long long
#define INF 0x3f3f3f
using namespace std;
int x,y,z;
signed main(){
	cin>>x>>y>>z;
	if(x+y<=z)cout<<"N";
	else cout<<"Y";
	return 0;
}

Python :

# coding=utf-8
x,y,z=map(float,input().split())
min=(x-y)**2
min=min**0.5/2
max=(x+y)/2
if(min<z and z<max):
    print('Y')
else:
    print('N')