View Compilation Error

0_0_2935976_8155.cpp: In function `int main()':
0_0_2935976_8155.cpp:8: error: `r' undeclared (first use this function)
0_0_2935976_8155.cpp:8: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_2935976_8155.cpp:8: error: `c' undeclared (first use this function)
0_0_2935976_8155.cpp:8: error: `n' undeclared (first use this function)