View Compilation Error

287120_0_491.cpp: In function `int main()':
287120_0_491.cpp:5: error: `n' undeclared (first use this function)
287120_0_491.cpp:5: error: (Each undeclared identifier is reported only once for each function it appears in.)
287120_0_491.cpp:10: error: `str' undeclared (first use this function)
287120_0_491.cpp:11: error: `sum' undeclared (first use this function)
287120_0_491.cpp:12: error: `len' undeclared (first use this function)
287120_0_491.cpp:13: error: `i' undeclared (first use this function)