Problem:
Score: 300 points

Problem Statement

Find the minimum prime number greater than or equal to X.

Notes

A prime number is an integer greater than 1 that cannot be evenly divided by any positive integer except 1 and itself.

For example, 2, 3, and 5 are prime numbers, while 4 and 6 are not.

Constraints

2 \le X \le 10^5

All values in input are integers.

Input

Input is given from Standard Input in the following format:

X

Output

Print the minimum prime number greater than or equal to X.

Sample Input 1

20

Sample Output 1

23

The minimum prime number greater than or equal to 20 is 23.

Sample Input 2

2

Sample Output 2

2

X itself can be a prime number.

Sample Input 3

99992

Sample Output 3

100003

Solution in C (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <float.h>
 
#pragma region 定義
#define i_cin(X) scanf("%d", &X)
#define i_cin2(X,Y) scanf("%d %d",&X,&Y)
#define i_cin4(X,Y,Z,W) scanf("%d %d %d %d",&X,&Y,&Z,&W)
#define i_cin3(X,Y,Z) scanf("%d %d %d",&X,&Y,&Z)
#define l_cin(X) scanf("%ld",&X)
#define f_cin(X) scanf("%f",&X)
#define l_cin2(X,Y) scanf("%ld %ld",&X,&Y)
#define s_cin(X) scanf("%s",&X)
#define ll_cin(X) scanf("%lld", &X)
 
#define  i_cout(X) printf("%d\n",X)
#define  f_cout(X) printf("%g\n",X)
#define  i_cout2(X,Y) printf("%d %d\n",X,Y)
#define  l_cout(X) printf("%ld\n",X)
#define  s_cout(X) printf("%s\n",X)
#define  ll_cout(X) printf("%lld\n",X)
 
typedef long long  ll;
#define rept(x, s, n) for (int x = s; x < n; x++)
 
#define S_RTN(S)  s_cout(S);return 0
 
 
#define _itoa(A,N) sprintf(A, "%d", N);
 
int i_cins(int n, int* A);
int l_cins2(int n, long* A, long* B);
int s_dsort(const void* a, const void* b);
int s_asort(const void* a, const void* b);
 
int  _gcd(int a, int b);
int  _swp(int* a, int* b);
int _cknum(char* a, int n);
int _atoi(char* s, int len);
 
 
int s_asorts(const void* a, const void* b);
 
//昇順
int s_asorts(const void* a, const void* b) {
    return(strcmp((char*)a, (char*)b));
}
int s_dsort(const void* a, const void* b) {
    return(*(int*)b - *(int*)a);
}
int s_asort(const void* a, const void* b) {
    return(*(int*)a - *(int*)b);
}
int l_cins2(int n, long* a, long* b) {
    int i;
    rept(i, 0, n) {
        l_cin2(*(a + i), *(b + i));
    }
    return 0;
}
int i_cins(int n, int* a) {
    int i;
    for (i = 0; i < n; i++) {
        i_cin(*(a + i));
    }
 
    return 0;
}
int _gcd(int a, int b) {
    int r, tmp;
    if (a < b) { tmp = a; a = b; b = tmp; }
    r = a % b;
    while (r) {
        if (!r) break;
        a = b; b = r;
        r = a % b;
    }
    return(b);
}
 
long _max(long a, long b) {
    return a > b ? a : b;
}
long _min(long a, long b) {
    return a < b ? a : b;
}
int _swp(int* a, int* b)
{
    int tmp;
    tmp = *b; *b = *a; *a = tmp;
    return 0;
}

//小さい順
int compare_int(const void *a, const void *b)
{
    return *(int*)b - *(int*)a;
}





int main(){
    int X;
    int temp=0;
    i_cin(X);
    while(1){
        int cnt=0;
        rept(i,2,X+1){
            temp=X%i;
            if(temp==0){
                cnt++;
            }
        }
        if(cnt==1){
            printf("%d",X);
            return 0;
        }
        X++;
    }
}