#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <climits>
#include <cstring>
#include <string>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <vector>
#include <list>
#define rep(i,m,n) for(i=m;i<=n;i++)
#define rsp(it,s) for(set<int>::iterator it=s.begin();it!=s.end();it++)
#define mod 2009
#define INF 9999999999999
#define vi vector<int>
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define pi acos(-1.0)
#define pii pair<int,int>
#define Lson L, mid, rt<<1
#define Rson mid+1, R, rt<<1|1
const int maxn=5e2+10;
using namespace std;
typedef long long ll;
ll gcd(ll p,ll q){return q==0?p:gcd(q,p%q);}
ll qpow(ll p,ll q){ll f=1;while(q){if(q&1)f=f*p;p=p*p;q>>=1;}return f;}
ll my_min(ll x,ll y){ return x>y?y:x;};
int main()
{
int m;
char str[100];
while(scanf("%d",&m)!=EOF)
{
int hour;
int sec;
scanf("%s",str);
hour = (str[0]-'0')*10+(str[1]-'0');
sec = (str[3]-'0')*10+(str[4]-'0');
if(m==12)
{
if(hour==0)
{
str[1] = '1';
}
else if(hour > 12)
{
if(str[1]=='0')
{
str[0]='1';
}
else
{
str[0] = '0';
}
}
}
else
{
if(hour>=24)
{
str[0]= '0';
}
}
if(sec>=60)
{
str[3]='0';
}
printf("%s\n",str);
}
return 0;
}