Exercício Concurso de dança

#include<stdio.h>
#include<stdlib.h>

typedef struct Casal{
    int cod;
    char ent[16];
}casal;

void escrever1 (){
    int n, i;
    FILE* fp;
    casal x;
    fp= fopen("concurso.cad", "wb");
    if(fp==NULL){
        printf("ERRO!");
        exit(1);
    }
    printf("\nDigite a quantidade de casais: ");
    scanf("%d", &n);
    fwrite(&n, sizeof(int), 1, fp);
    for(i=0; i<n; i++){
        printf("\nDigite o codigo do casal: ");
        scanf("%d", &x.cod);
        printf("\nDigite a entidade do casal: ");
        scanf("%s", &x.ent);
        fwrite(&x, sizeof(casal), 1, fp);
    }
    fclose(fp);
}

void escrever2 (){
    FILE* fp, *av;
    int i, n;
    casal x;
    float cav, dam, med;
    fp = fopen("concurso.cad", "rb");
    av = fopen("concurso.not", "wb");
    fread(&n, sizeof(int), 1, fp);
    fwrite(&n, sizeof(int), 1, av);
    for(i=0; i<n; i++){
        fread(&x, sizeof(casal), 1, fp);
        printf("\nCodigo: %d", x.cod);
        fwrite(&x, sizeof(casal), 1, av);
        printf("\nDigite a nota da dama: ");
        scanf("%f", &dam);
        fwrite(&dam, sizeof(float), 1, av);
        printf("\nDigite a nota do cavalheiro: ");
        scanf("%f", &cav);
        fwrite(&cav, sizeof(float), 1, av);
        med= (dam + cav)/2.0;
        fwrite(&med, sizeof(float), 1, av);
    }
    fclose(fp);
    fclose(av);
}

void Ler(){
    FILE* rd;
    int i, n;
    casal x;
    float cav, dam, med;
    rd = fopen("concurso.not", "rb");
    fseek (rd, 0, SEEK_SET);
    fread(&n, sizeof(int), 1, rd);
    for(i=0; i<n; i++){
        fread(&x, sizeof(casal), 1, rd);
        printf("\nCodigo: %d\nEntidade: %s", x.cod, x.ent);
        fread(&dam, sizeof(float), 1, rd);
        printf("\nNota da dama: %.2f", dam);
        fread(&cav, sizeof(float), 1, rd);
        printf("\nNota do cavalheiro: %.2f", cav);
        fread(&med, sizeof(float), 1, rd);
        printf("\nNota media: %.2f\n", med);
    }
    fclose(rd);
}

int main(){
    escrever1();
    escrever2();
    Ler();
}