#include #include using namespace std; int main(){

while (true) { int n; double a,b,c; char f; cout<"请输入你要保留的小数位数:"; cin>n;

cout<<endl<<"请输入算式:";
cin>>a>>f>>b;
if(f=='+'){
	c=a+b;
}
if(f=='-'){
	c=a-b;
}else if(f=='*'){
	c=a*b;
}else if(f=='/'){
	c=a/b;
}
cout<<fixed<<setprecision(n)<<c<<endl<<"——————————————————————————————————————————"<<endl;

} }