# Program to check Friendly pair

## what is friendly pair :-

Two number n1 and n2 is said to friendly if (sum of divisor of n1/ n1 ) is equal to the (sum of divisor of n2/ n2) .

For example: –

(sum of divisors of 6 / 6 ) = (sum of divisors of 28 / 28)

(1+2+3)/6 = (1+2+4+7+14)/28

1 = 1

so (6,28) is a friendly pair.

## Program to check Friendly pair :-

C++ Code:-

```#include<bits/stdc++.h>
using namespace std;
int main()
{
int n1,n2,sum_d1=0,sum_d2=0;
cout<<"Enter first number"<<endl;
cin>>n1;
cout<<"Enter second number"<<endl;
cin>>n2;

//find sum of divisors of first number
for(int i=1;i<n1;i++)
{
if(n1%i==0)
sum_d1+=i;

}
//find sum of divisors of second number
for(int i=1;i<n2;i++)
{
if(n2%i==0)
sum_d2+=i;

}

if((sum_d1/n1)==(sum_d2/n2))
cout<<"friendly pair"<<endl;
else
cout<<"Not a friendly pair"<<endl;

return 0;
}```

Output:-

```Enter first number
6
Enter second number
28
friendly pair```

python code:-

```def checkperfect(x):
sum=0
for i in range(1,x):
if x%i==0:
sum=sum+i
if sum==x:
return 1
else:
return 0
a,b=map(int,input().split())
r1=checkperfect(a)
r2=checkperfect(b)
if r1==1 and r2==1:
print("Yes, they are friendly pair" )
else:
print("No, they are not friendly pair")
```

output:-

```6 28
Yes, they are friendly pair```