You define the variable s as plastic, but the assignment is double-precision floating-point type. This is definitely not right. It should be defined as follows:

Double Fund (International) {

int a =2，b= 1，c，k；

Double s = 0.0

s = s+(double)a/b；

}

Return to s; //You can add brackets here or not. . .

The function you define is a double-precision floating-point type, so the return value should also be a double-precision floating-point type, and the return value should be outside the braces.