int s3(int *a,int s2,int e1,int s1,int e2,int* m1,int* m2);

int s4(int* a,int l){
    int s=0, *m1=(int *)malloc(l*sizeof(int)), *m2=(int *)malloc(l*sizeof(int));
    if(!m1&&!m2)return -1;
    while (s<l) {
        int i,s1,e1,s2,e2;
        for(i=0;(i+s-1)<(l-1);i+=2*s){
            s1=i;
            e1=i+s-1;
            s2=e1+1;
            (i+2*s-1)<(l-1)?(e2=i+2*s-1):(e2=l-1);
            s3(a,s1,e1,s2,e2,m1,m2);
        }
    s=s<<1;
    }
    return 0;
}

int s3(int *a,int s1,int e2,int s2,int e1,int* m1,int* m2){
    int l1=e1-s1+1, ll=e2-s2+1, p1=0, p2=0, p=s1;
    for(unsigned i = 0; i < l1; ++i) m1[i] = (a+s1)[i];
    for(unsigned i = 0; i < ll; ++i) m2[i] = (a+s1)[i];
    while (p1<l1&&p1<ll) if(m1[p1]<m2[p2])a[p++]=m1[p1++]; else a[p++]=m2[p2++];
    while (p1<l1) a[p++]=m1[p1++];
    while(p2<ll) a[p++]=m2[p2++];
    return 0;
}

int main(){
    int a[10]={8,9,20,0,3,20,0};
    int l=10;
    s4(a,l);

    int i;
    for (i=0;i<l;i++)printf("%d\t",a[i]);
    printf("\n");
    return 0;
}