#include<cstdio>
#include<iostream>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<cmath>
#include<vector>
using namespace std;
int read()
{int x=0,f=1;char ch=getchar();while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}while('0'<=ch&&ch<='9'){x=x*10+ch-'0';ch=getchar();}return x*f;
}
int readtime()
{int ret=0;for(int i=1,b=3600;i<=3;i++,b/=60){int k=0;char ch;ch=getchar();while(ch<'0'||ch>'9')ch=getchar();k=ch-'0';ch=getchar();k=k*10+ch-'0';ret+=k*b;}return ret;
}
void writetime(int T)
{int k=T/3600;T-=k*3600;if(k<10)printf("0");printf("%d",k);k=T/60;T-=k*60;if(k<10)printf("0");printf("%d",k);if(T<10)printf("0");printf("%d\n",T);
}//-----------------------------------------------------------------------------------------------------struct car
{int st,t;car(){}car(int ST,int T){st=ST,t=T;}
}c[310];int L[60],R[60];
int f[60][110000];
int main()
{freopen("a.in","r",stdin);freopen("a.out","w",stdout);int n,m,x,st,t;n=read(),m=read();for(int i=1;i<=n;i++)L[i]=m+1;for(int i=1;i<=m;i++){x=read(),c[i].st=readtime(),c[i].t=read();if(L[x]==m+1)L[x]=i;R[x]=i;}memset(f,63,sizeof(f));f[1][21600]=0;for(int i=1;i<n;i++)for(int j=21600;j<86400;j++)if(f[i][j]!=f[0][0]){for(int k=300;k<=600;k++){if(j+k>=86400)break;int sum=0;for(int l=L[i];l<=R[i];l++)if((j+k==c[l].st+c[l].t)||(j<c[l].st&&j+k>=c[l].st+c[l].t)||(j>c[l].st&&j+k<=c[l].st+c[l].t))sum++;f[i+1][j+k]=min(f[i+1][j+k],f[i][j]+sum);}}int mmin=(1<<30),T;for(int j=21600;j<86400;j++)if(f[n][j]<mmin)mmin=f[n][j],T=j;printf("%d\n",mmin);writetime(T);return 0;
}