Compilare: user.cpp:3:68: warning: ISO C++ forbids declaration of ‘main’ with no type [-Wreturn-type] using namespace std;int i ,n ,r ,u=-110;pair<int,int> x[8001];main(){FILE *f1;fscanf((f1=fopen("reactivi.in","r")),"%d",&n);for(i=1;i<=n;++i)fscanf(f1,"%d%d",&x[i].second,&x[i].first);sort(x+1,x+n+1);for(i=1;i<=n;i++)if(u<x[i].second){u=x[i].first;r++;}fprintf(fopen("reactivi.out","w"),"%d",r);return 0;} ^ user.cpp: In function ‘int main()’: user.cpp:3:124: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] using namespace std;int i ,n ,r ,u=-110;pair<int,int> x[8001];main(){FILE *f1;fscanf((f1=fopen("reactivi.in","r")),"%d",&n);for(i=1;i<=n;++i)fscanf(f1,"%d%d",&x[i].second,&x[i].first);sort(x+1,x+n+1);for(i=1;i<=n;i++)if(u<x[i].second){u=x[i].first;r++;}fprintf(fopen("reactivi.out","w"),"%d",r);return 0;} ^ user.cpp:3:184: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] using namespace std;int i ,n ,r ,u=-110;pair<int,int> x[8001];main(){FILE *f1;fscanf((f1=fopen("reactivi.in","r")),"%d",&n);for(i=1;i<=n;++i)fscanf(f1,"%d%d",&x[i].second,&x[i].first);sort(x+1,x+n+1);for(i=1;i<=n;i++)if(u<x[i].second){u=x[i].first;r++;}fprintf(fopen("reactivi.out","w"),"%d",r);return 0;} ^