Main.cc: In function 'int main()': Main.cc:11:5: error: expected initializer before 'for' for(int i=0;i=a[i-1]&&a[i]-a[i-1]<=2){ ^ Main.cc:22:9: error: expected ';' before '}' token } ^ Main.cc:8:15: warning: unused variable 'b' [-Wunused-variable] int n,m=0,b,ma=0; ^