#include <iostream>
#include <sstream>
#include <limits>
int main()
{
std::istringstream stm( "A: 10\n"
"B: 20\n"
"C: 30\n" ) ;
constexpr char delimiter = ':' ;
const auto max = std::numeric_limits<std::streamsize>::max() ;
int number ;
while( stm.ignore( max, delimiter ) >> number ) std::cout << number << '\n' ;
}
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