Compilare: main.cpp: In function 'int main()': main.cpp:2:283: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] using namespace std;int v1[100010];vector<int>v[100010];int main(){int n,i,x=0,j,a,b;freopen("heavymetal.in","r",stdin);freopen("heavymetal.out","w",stdout);scanf("%d",&n);for(i=1;i<=n;i++){scanf("%d%d",&a,&b);v[b].push_back(a);x=max(x,b);}for(i=1;i<=x;i++){v1[i]=v1[i-1];for (j=0;j<v[i].size();j++)v1[i]=max(v1[i],v1[v[i][j]]+i-v[i][j]);}printf("%d",v1[x]);return 0;} ~^~~~~~~~~~~~ main.cpp:2:120: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] using namespace std;int v1[100010];vector<int>v[100010];int main(){int n,i,x=0,j,a,b;freopen("heavymetal.in","r",stdin);freopen("heavymetal.out","w",stdout);scanf("%d",&n);for(i=1;i<=n;i++){scanf("%d%d",&a,&b);v[b].push_back(a);x=max(x,b);}for(i=1;i<=x;i++){v1[i]=v1[i-1];for (j=0;j<v[i].size();j++)v1[i]=max(v1[i],v1[v[i][j]]+i-v[i][j]);}printf("%d",v1[x]);return 0;} ^ main.cpp:2:157: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] using namespace std;int v1[100010];vector<int>v[100010];int main(){int n,i,x=0,j,a,b;freopen("heavymetal.in","r",stdin);freopen("heavymetal.out","w",stdout);scanf("%d",&n);for(i=1;i<=n;i++){scanf("%d%d",&a,&b);v[b].push_back(a);x=max(x,b);}for(i=1;i<=x;i++){v1[i]=v1[i-1];for (j=0;j<v[i].size();j++)v1[i]=max(v1[i],v1[v[i][j]]+i-v[i][j]);}printf("%d",v1[x]);return 0;} ^ main.cpp:2:172: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] using namespace std;int v1[100010];vector<int>v[100010];int main(){int n,i,x=0,j,a,b;freopen("heavymetal.in","r",stdin);freopen("heavymetal.out","w",stdout);scanf("%d",&n);for(i=1;i<=n;i++){scanf("%d%d",&a,&b);v[b].push_back(a);x=max(x,b);}for(i=1;i<=x;i++){v1[i]=v1[i-1];for (j=0;j<v[i].size();j++)v1[i]=max(v1[i],v1[v[i][j]]+i-v[i][j]);}printf("%d",v1[x]);return 0;} ^ main.cpp:2:210: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] using namespace std;int v1[100010];vector<int>v[100010];int main(){int n,i,x=0,j,a,b;freopen("heavymetal.in","r",stdin);freopen("heavymetal.out","w",stdout);scanf("%d",&n);for(i=1;i<=n;i++){scanf("%d%d",&a,&b);v[b].push_back(a);x=max(x,b);}for(i=1;i<=x;i++){v1[i]=v1[i-1];for (j=0;j<v[i].size();j++)v1[i]=max(v1[i],v1[v[i][j]]+i-v[i][j]);}printf("%d",v1[x]);return 0;} ^