PAT 1006 sign in and sign out

#include<cstdio>
#include<cstring>
using namespace std;
char firstper[20];
char lastper[20];
char firsttime[20]="23:59:59";
char lasttime[20]="00:00:00";

int main(){
    int n;
    scanf("%d",&n);
    char id[20],in[20],out[20];
    while(n--){
        scanf("%s%s%s",id,in,out);
        if(strcmp(in,firsttime)<0){
            strcpy(firsttime,in);
            strcpy(firstper,id);
        }
        if(strcmp(out,lasttime)>0){
            strcpy(lasttime,out);
            strcpy(lastper,id);
        }

    }
    printf("%s %s",firstper,lastper);
}