C :

#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>

int fun(int x)
{
    int flag =0;
    int i;
    for( i =2; i <x;i++)
    {
        if(x % i == 0)
            break;
    }
    if(i == x)
        flag =1;
    return flag;
}

int main()
{
   // freopen("in","r",stdin);
  // freopen("out","w",stdout);

   int n ;

    while(scanf("%d",&n)!=EOF)
    {
        do
        {
            n++;
        }while(!fun(n));
        printf("%d\n",n);
    }

	return 0;

}

C++ :

#include<stdio.h>
int main()
{
	int i,j,n;
		while(scanf("%d",&n)!=EOF)
		{
			for(i=n+1;i<i+1;i++)
			{
				for(j=2;j<i;j++)
				{
					if(i%j==0)
						break;
					if(j==i-1)
					{
						printf("%d\n",i);
						break;
					}
				}
				if(j==i-1)
					break;
			}
		}
		return 0;
}