View Compilation Error

0_0_11573509_25264.cpp: In function `int main()':
0_0_11573509_25264.cpp:12: error: `foo' undeclared (first use this function)
0_0_11573509_25264.cpp:12: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_11573509_25264.cpp: In function `int foo(int)':
0_0_11573509_25264.cpp:20: error: `int foo(int)' used prior to declaration