${\int }_0^{1}f\left(x\right)dx=\sum _{i=0}^{\infty }{x}_i=\prod _{i=0}^{\infty }{x}_i=\coprod _{i=0}^{\infty }{x}_i={\oint }_0^{1}f\left(x\right)dx={\iint }_0^{1}f\left(x\right)dx={\iiint }_0^{1}f\left(x\right)dx$