program sum(input,output);{1$B!\(B2$B!\(B...$B!\$N7W;;(B} var n,m,i:integer; sum:longreal; begin write(output,'n (>0) ? '); readln(input,m,n); sum:=0; for i:=m to n do sum:=sum+i; writeln(output,m:1,'+',m+1:1,'+...+',n:1, '=',sum:20); end.