I am getting compilation error, but I CAN compile it?

#include <fstream.h>
#include <stdlib.h>
#include <mem.h>
//ifstream fin("square.dat");
short l,a,m, imp[100],size[100],x[100],y[100];
char f[10001]; short s[2][10001];

inline short min3(short a, short b, short c)
{
    return a<b ? (a<c?a:c) : (b<c?b:c);
}

void trace(int r, int u)
{
    int i,j,g;
    memset(f+1,1,l);
    for(i=0; i<m; i++) if(imp[i]>u && y[i]<=r && r<y[i]+size[i])
    {
        g=x[i]+size[i];
        for(j=x[i]; j<g; j++) f[j]=0;
    }
}

void find(int u)
{
    int i,j,b1,b0;
    trace(1,u);
    if(a==1)
        for(i=1; i<=l; i++)
        {
            if(f[i]) {cout << u << endl; exit(0);}
            s[1][i]=0;
        }
    else
        for(i=1; i<=l; i++)s[1][i]=f[i];

    for(j=2; j<=l; j++)
    {
        b1=j&1; b0=1-b1;
        s[b1][0]=0; trace(j,u);

        for(i=1; i<=l; i++)
            if(f[i])
            {
                s[b1][i] = 1+min3(s[b1][i-1],s[b0][i],s[b0][i-1]);
                if(s[b1][i]==a) {cout << u << endl; exit(0);}
            }
            else
                s[b1][i] = 0;
    }
}

void main()
{
    cin >> l >> a >> m;
    char z[101]={0,1};
    for(int i=0; i<m; i++) {cin >> imp[i] >> size[i] >> x[i] >> y[i]; z[imp[i]]=1;}
    for(i=1; i<=100; i++) if(z[i]) find(i);
    cout << "IMPOSSIBLE" << endl;
}