Compilare: main.cpp: In function 'int main()': main.cpp:2:74: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] int mat[1001][5];int main(){int n,k,i,j,i2,a;freopen("div3.in","r",stdin);freopen("div3.out","w",stdout);scanf("%d%d",&n,&k);for(i=1;i<=n;i++)scanf("%d",&a),mat[1][a%3]++;for(i=2;i<=k;i++)for(j=0;j<=2;j++)for(i2=0;i2<=2;i2++)mat[i][(j+i2)%3]=(mat[i][(j+i2)%3]+mat[i-1][j]*mat[1][i2])%4001;printf("%d",mat[k][0]);} ^ main.cpp:2:105: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] int mat[1001][5];int main(){int n,k,i,j,i2,a;freopen("div3.in","r",stdin);freopen("div3.out","w",stdout);scanf("%d%d",&n,&k);for(i=1;i<=n;i++)scanf("%d",&a),mat[1][a%3]++;for(i=2;i<=k;i++)for(j=0;j<=2;j++)for(i2=0;i2<=2;i2++)mat[i][(j+i2)%3]=(mat[i][(j+i2)%3]+mat[i-1][j]*mat[1][i2])%4001;printf("%d",mat[k][0]);} ^ main.cpp:2:125: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] int mat[1001][5];int main(){int n,k,i,j,i2,a;freopen("div3.in","r",stdin);freopen("div3.out","w",stdout);scanf("%d%d",&n,&k);for(i=1;i<=n;i++)scanf("%d",&a),mat[1][a%3]++;for(i=2;i<=k;i++)for(j=0;j<=2;j++)for(i2=0;i2<=2;i2++)mat[i][(j+i2)%3]=(mat[i][(j+i2)%3]+mat[i-1][j]*mat[1][i2])%4001;printf("%d",mat[k][0]);} ^ main.cpp:2:171: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] int mat[1001][5];int main(){int n,k,i,j,i2,a;freopen("div3.in","r",stdin);freopen("div3.out","w",stdout);scanf("%d%d",&n,&k);for(i=1;i<=n;i++)scanf("%d",&a),mat[1][a%3]++;for(i=2;i<=k;i++)for(j=0;j<=2;j++)for(i2=0;i2<=2;i2++)mat[i][(j+i2)%3]=(mat[i][(j+i2)%3]+mat[i-1][j]*mat[1][i2])%4001;printf("%d",mat[k][0]);} ^