param N;
param M;
param J{1..N};
param d{1..M};
param s{1..M};
param R{1..M};

var I{1..M};

minimize f: sum{e in 1..M} 0.5*R[e]*I[e]^2;

s.t. g {k in 1..N} : J[k] + sum{e in 1..M : s[e]= k} I[e] = sum{e in 1..M : d[e]= k} I[e];