C++ :

#include<bits/stdc++.h>
using namespace std;
long long  n,m,l;
int a;
int main()
{
cin>>n;
for(m=1;m<=n;m*=10);
l=n*n;
l=l%m;
if(l==n)
	cout<<"YES";
else
	cout<<"NO";	
return 0;
}

Python :

# coding=utf-8
n=int(input())
if 1<n<10:
    t=n*n
    if t%10==n:
        print("YES")
    else:
        print("NO")

if 10<n<100:
    t=n*n
    if t%100==n:
        print("YES")
    else:
        print("NO")
if 100<n<1000:
    t=n*n
    if t%1000==n:
        print("YES")
    else:
        print("NO")
if 1000<n<10000:
    t=n*n
    if t%10000==n:
        print("YES")
    else:
        print("NO")
if 10000<n<100000:
    t=n*n
    if t%100000==n:
        print("YES")
    else:
        print("NO")
if 100000<n<1000000:
    t=n*n
    if t%1000000==n:
        print("YES")
    else:
        print("NO")
if 1000000<n<10000000:
    t=n*n
    if t%10000000==n:
        print("YES")
    else:
        print("NO")
if 10000000<n<100000000:
    t=n*n
    if t%100000000==n:
        print("YES")
    else:
        print("NO")