Write a CPP function to find next prime number of a given number

 Code:-

#include<bits/stdc++.h>

using namespace std;

// function for checking prime number

int prime(int n)

{

int flag=0,i;

for(i=2;i<=n/2;i++)

{

if(n%i==0)

{

flag=1;

break;

}

}

if(flag==1)

return 1;

else

return 0;

}

// Driver function

int main()

{

int a,f=1,b;

cout<<"Enter a number : ";

cin>>a;

b=a; // Copy a into b for future use

while(f)

{

a++;

f=prime(a);

}

cout<<"Next prime number of "<<b<<" is : "<<a;

return 0;

}

Output:-

Enter a number : 15

Next prime number of 15 is : 17