问个简单的（12小时转至24小时制）：这个哪里错了？

#include"iostream"
using namespace std;
void input(int &hours24,int &minutes)
{
cin>>hours24>>":">>minutes;
}
void convert(int&hours,char&AMPM)
{
if(hours-12<0)AMPM='A';
else
{
hours-=12;
AMPM='P';
}
}
void output(int hours,int minutes,char AMPM)
{
cout<<hours<<":"<<minutes<<AMPM<<endl;
}
void main()
{
int hours24,minutes;
char AMPM;
input(&hours24,&minutes);
convert(&hours24,&AMPM);
output(hours24,minutes, AMPM);
}

 #include<iostream>

using namespace std;

void input(int &hours24,int &minutes)
{
    char tmp;
    cin>>hours24>>tmp>>minutes;
}

void convert(int&hours,char&AMPM)
{
    if(hours-12<0)AMPM='A';
    else
    {
        hours-=12;
        AMPM='P';
    }
}

void output(int hours,int minutes,char AMPM)
{
    cout<<hours<<":"<<minutes<<AMPM<<endl;
}

int main()
{
    int hours24,minutes;
    char AMPM;
    input(hours24,minutes);
    convert(hours24,AMPM);
    output(hours24,minutes, AMPM);
}